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 Showing results 1 to 25 of 526 Search took 0.08 seconds. Search: Posts Made By: enzocreti
 Forum: enzocreti 2020-09-30, 13:44 Replies: 2 Views: 196 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: 87 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: 104 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: 420 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: 531 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: 531 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: 531 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: 531 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: 531 Posted By enzocreti Unfortunally my computer is broken! Unfortunally my computer is broken!
 Forum: enzocreti 2020-08-31, 11:27 Replies: 20 Views: 531 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: 610 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: 610 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: 610 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: 610 Posted By enzocreti 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: 240 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: 2,447 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: 414 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: 384 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: 1,234 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: 1,234 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: 423 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: 1,234 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: 1,234 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: 1,234 Posted By enzocreti 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...
 Forum: enzocreti 2020-06-14, 08:04 Replies: 2 Views: 480 Posted By enzocreti 512 Is 512 the only cube with the property that if the digits are reversed, the reverse 215 is a cube minus one?
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