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Search: Posts Made By: enzocreti
Forum: enzocreti 2020-10-27, 13:01
Replies: 10
Views: 241
Posted By enzocreti
a difficult problem

Let be N a nonnegative integer.


I search integers N such that


N+20=s^2*p and N+19=q^2*(2*p+1), where s and q are integers>1 and p is a prime>2 and (2p+1) is a prime as well.
Forum: enzocreti 2020-09-30, 13:44
Replies: 2
Views: 232
Posted By enzocreti
How to proof that numbers 18, 108, 1008,...will never be divisible by 6^4?

How to proof that numbers of the form 18, 108, 1008, 10008, 100008, 1000...0008 will never be divisible by 6^4?
Forum: enzocreti 2020-09-29, 14:46
Replies: 1
Views: 111
Posted By enzocreti
Is 56238 the only N with this property?

Is 56238 the only positive integer N such that


sigma(N)/546=2^j, where j is a positive integer?


sigma is the sum of the divisors of N
Forum: enzocreti 2020-09-29, 09:26
Replies: 3
Views: 133
Posted By enzocreti
sigma(n)=x*(x+1)^3

let be sigma(n) the sum of the divisors of n




something is known about numbers n such that


sigma(n)=x*(x+1)^3 with x positive integer?
Forum: enzocreti 2020-09-01, 08:43
Replies: 3
Views: 506
Posted By enzocreti
...factorial(n) plus/minus 1 is semiprime

Is there an Oeis sequence dedicated to numbers n such that n!+1 and n!-1 are both semiprime? An example is 20970


Infact 20970!+1 is semiprime and also 20970!-1 is semi prime




No the...
Forum: enzocreti 2020-09-01, 07:53
Replies: 20
Views: 623
Posted By enzocreti
...i did not...

i did not take into account that N must be 10^m mod 41




let's guess congruent to 1 mod 41
Forum: enzocreti 2020-09-01, 07:32
Replies: 20
Views: 623
Posted By enzocreti
...not that's not prp

how about this:


(2^1430136-1)*10^430514+2^1430135-1???


I made a stupid mistacke


the candidates have the form
Forum: enzocreti 2020-09-01, 07:21
Replies: 20
Views: 623
Posted By enzocreti
...but this is almost surely PRP!

(2^3680800-1)*10^1108031+2^3680799-1
Forum: enzocreti 2020-08-31, 15:43
Replies: 20
Views: 623
Posted By enzocreti
Pg(69660) is prime 69660 is multiple of...

Pg(69660) is prime


69660 is multiple of 215 and congruent to 215 mod 323...it is also 6 mod 13... using wolphram numbers of this form are 69660+xn where x i don't remember what it is.

69660...
Forum: enzocreti 2020-08-31, 13:52
Replies: 20
Views: 623
Posted By enzocreti
Unfortunally my computer is broken!

Unfortunally my computer is broken!
Forum: enzocreti 2020-08-31, 11:27
Replies: 20
Views: 623
Posted By enzocreti
probable dud

((2^1875230-1)*10^564501+2^1875229-1) has small factors?


I don't know...:smile:
Forum: enzocreti 2020-08-29, 08:01
Replies: 11
Views: 690
Posted By enzocreti
... 56238...

56238 is a not palindromic number such that the reverse 83265 (squarefree) also belongs to Oeis sequence A165256. Are there other examples of not palindromic numbers belonging to A165256 whose...
Forum: enzocreti 2020-08-28, 18:02
Replies: 11
Views: 690
Posted By enzocreti
Are 56238 and 75894 the only multiple of 546...

Are 56238 and 75894 the only multiple of 546 squarefree belonging to the sequence A165256 ?
Forum: enzocreti 2020-08-28, 16:42
Replies: 11
Views: 690
Posted By enzocreti
... 75894...

Pg(56238) is prime and also pg(75894) is prime

56238 and 75894 are multiple of 546.

56238 and 75894 are square free and belong to the Oeis sequence you mentioned


Pg(n) is the concatenation...
Forum: enzocreti 2020-08-28, 14:46
Replies: 11
Views: 690
Posted By enzocreti
rolleyes numbers of yet another particular type

Consider numbers N squarefree that is in the factorisation of N there is no prime facor raised to a power greater than 1.




56238 is square free


56238 has five digits
Forum: enzocreti 2020-08-27, 07:50
Replies: 0
Views: 277
Posted By enzocreti
ec exponents in position 9n

a(9)=36
a(18)=1323
a(27)=69660
a(36)=360787



pg(36), pg(1323) and pg(69660) and pg(360787) are primes
Forum: enzocreti 2020-08-19, 05:48
Replies: 8
Views: 2,546
Posted By enzocreti
Q77I 215 69660 92020 541456 are...

Q77I


215 69660 92020 541456 are congruent to plus or minus (6^k-1) mod 323 for k=3,2


69660=(2^5*3^7)-(2^3*3^4) so it is the difference of two 3 smooth numbers (2^a*3^b)-(2^(a-3)*3^(b-3))
Forum: enzocreti 2020-07-23, 07:33
Replies: 0
Views: 490
Posted By enzocreti
pg(308899)

pg(69660) is prime
pg(92020) is prime and 92020+239239 is prime
pg(92020+239239) is prime




Now i consider
Forum: enzocreti 2020-07-02, 09:29
Replies: 0
Views: 441
Posted By enzocreti
collatz 3x+1

I found a forumula about the 3x+1 problem


let be T(k,n) the trajectory starting from integer n.


k is the number of iterations


T(0,n)=n i think
Forum: enzocreti 2020-06-21, 22:01
Replies: 4
Views: 1,309
Posted By enzocreti
Pg(69660) pg(92020) and pg(541456) pg(k) primes with k multiple of 86

This identity involves pg(k) primes with k multiple of 86

k multiple of 86 with pg(k) primes satisfy this identity

541456-(69660*16/10+1000)=1000*sqrt(92020*2+1)


pg(366770) is prime and...
Forum: enzocreti 2020-06-20, 17:55
Replies: 4
Views: 1,309
Posted By enzocreti
Pg(6231) and pg(51456)

There are two primes pg(6231) and pg(51456) with 6231 and 51456 multiple of 201

51456(even)=201*(2^8)
6231(odd)=201*(2^5-1)

Pg(541456) is probab prime

541456=(46^2-1)*2^8+2^4
Forum: enzocreti 2020-06-19, 21:12
Replies: 0
Views: 463
Posted By enzocreti
Lcm(344,559) 331 and pg primes

Pg(215), pg(69660),pg(92020) pg(541456) are prp with 215, 69660, 92020 and 541456 multiple of 43.

215, 69660, 92020, 541456 are plus/minus 344 mod 559

lcm(344,559)=4472

4472=8*331+456*4
...
Forum: enzocreti 2020-06-18, 19:26
Replies: 4
Views: 1,309
Posted By enzocreti
Pg(92020) and pg(331259)

Pg(92020) and pg(331259) are probable primes

331259=92020+239239

92020 and 331259 are congruent to 5 mod ((331+456*6)*6+1) where 3067=331+456*6 is a prime
Forum: enzocreti 2020-06-17, 10:45
Replies: 4
Views: 1,309
Posted By enzocreti
Pg(92020) pg(69660) and pg(541456)

Pg(92020) pg(69660) and pg(541456) are primes
92020 541456 69660 are 10^m mod 41 and multiple of 43

541456 is multiple of 787

92020 and 69660 are congruent to 10^s mod (787+456*r) for some...
Forum: enzocreti 2020-06-15, 10:24
Replies: 4
Views: 1,309
Posted By enzocreti
Smile Pg(75894) and pg(56238) and other random pg(x)

Pg(75894) and pg(56238) are primes or at least probable primes

I noticed that 75894 and 56248 are multiple of 546 and congruent to 24 mod 54

Using Wolphram (Chinese remainder theorem) I was...
Showing results 1 to 25 of 527

 
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