PARI's commands

[3.14159]

Primes p such that p*10² + 1 is also prime: 701, 1301, 1901, 3701, 6101, 6701, 7901, 10301, 13901, 15101, 16301, 19301, 21101, 22901, 27701, 42101, 46301, 52301, 54101, 60101, 64301, 70901, 72701, 81101, 82301, 87701, 88301, 93701, 102101, 112901, 115301, 117101, 123701, 132701, 138101, 139901, 144701, 148301, 157901, 159701, 165701, 166301, 174101, 178301, 186701, 193301, 198701, 201101, 201701, 217901, 220301, 226901, 237701, 243701, 247301, 250301, 252101, 253901, 270701, 285101, 291701, etc...

Submitted to OEIS.

[science_man_88]

Originally Posted by 3.14159

Primes p such that p*10² + 1 is also prime: 701, 1301, 1901, 3701, 6101, 6701, 7901, 10301, 13901, 15101, 16301, 19301, 21101, 22901, 27701, 42101, 46301, 52301, 54101, 60101, 64301, 70901, 72701, 81101, 82301, 87701, 88301, 93701, 102101, 112901, 115301, 117101, 123701, 132701, 138101, 139901, 144701, 148301, 157901, 159701, 165701, 166301, 174101, 178301, 186701, 193301, 198701, 201101, 201701, 217901, 220301, 226901, 237701, 243701, 247301, 250301, 252101, 253901, 270701, 285101, 291701, etc...

There should only be two sequences: One for p * 10ⁿ + 1, when n is any integer, and for 100.

so in other words p*10ⁿ+1 and p*10¹⁰⁰ +1 ?

or

p*10ⁿ+1 and p*100ⁿ+1 ?

[3.14159]

Former.

[science_man_88]

Originally Posted by 3.14159

There are no redundancies.

Not every square number is a fourth power. Fourth powers are a subset of squares.

Nevermind. This is getting me nowhere. Fine, you win. You can keep the smug expression on your face.

what CRG was saying is:

1,4,9,16,25,36,49,64,81,100,121,144,169,196,225,256,....

1,16,81,256,........

1) n²
2) n⁴
Red) the members in both sequences

see how all the n⁴ are Red ? since it includes all fourth powers only then it can be stated: within the set of fourth powers, instead of in the set of squares and the set of fourth powers, so the redundancy stays.

[3.14159]

Sent the b-file for the first 20000 terms. The 20000th term is 284727701.

[CRGreathouse]

Originally Posted by science_man_88

(13:45) gp > ifprime(x,p)=if(isprime(x),p)
%11 = (x,p)->if(isprime(x),p)
(13:47) gp > ifprime(100,print(100))
100

I was trying something like this but I can't get it to work. why ? is my best question.

Originally Posted by axn

ifprime(p, s)=if(isprime(p), eval(s));
ifprime(100, "print(p)");
ifprime(101, "print(p)");
101

Originally Posted by science_man_88

I should of known this by now lol thank you though in a way this is useless but it is useful in the fact that it could create shorter code when typing it in. as by the look of it it saves 10 characters I was also thinking of one where you can do a && part in the if I think I'll try that next.

Hats off to axn for understanding the request!

Another way to do it -- the way I'd prefer -- is to pass a closure rather than a string. So

ifprime(p, s)=if(isprime(p), s(p));
ifprime(100, p -> print(p));
ifprime(101, p -> print(p));

or even

ifprime(p, s)=if(isprime(p), s(p));
printme(n)=print(n);
ifprime(100, printme);
ifprime(101, printme);

[CRGreathouse]

Originally Posted by 3.14159

Primes p such that p*10² + 1 is also prime: 701, 1301, 1901, 3701, 6101, 6701, 7901, 10301, 13901, 15101, 16301, 19301, 21101, 22901, 27701, 42101, 46301, 52301, 54101, 60101, 64301, 70901, 72701, 81101, 82301, 87701, 88301, 93701, 102101, 112901, 115301, 117101, 123701, 132701, 138101, 139901, 144701, 148301, 157901, 159701, 165701, 166301, 174101, 178301, 186701, 193301, 198701, 201101, 201701, 217901, 220301, 226901, 237701, 243701, 247301, 250301, 252101, 253901, 270701, 285101, 291701, etc...

Submitted to OEIS.

"Primes p such that p*10² + 1 is also prime" are 7,13,19,37,61,67,79,103,.... "Primes p such that (p*10)² + 1 is also prime" are 2,11,13,17,23,43,47,89,101,.... I'm not sure what your sequence is!

You should probably discuss your sequences here before submitting so we can iron out the wording and so forth.

[science_man_88]

Originally Posted by CRGreathouse

"Primes p such that p*10² + 1 is also prime" are 7,13,19,37,61,67,79,103,.... "Primes p such that (p*10)² + 1 is also prime" are 2,11,13,17,23,43,47,89,101,.... I'm not sure what your sequence is!

You should probably discuss your sequences here before submitting so we can iron out the wording and so forth.

he's using p*10ⁿ+1 I believe for one thing he's checking and p*10¹⁰⁰ +1 for another I'm unsure about what he's posted as well for once.

[kar_bon]

No, he gave the values for p*10^2+1, but as stated "Primes p such..." should list the p-values and not the p*10^2+1 results!

The sequence as submitted is false!

[science_man_88]

Originally Posted by kar_bon

No, he gave the values for p*10^2+1, but as stated "Primes p such..." should list the p-values and not the p*10^2+1 results!

The sequence as submitted is false!

so in other terms:

forprime(p=1,1500,if(isprime(p*10^2+1),print(p*10^2+1)))

[science_man_88]

instead of :

forprime(p=1,1500,if(isprime(p*10^2+1),print(p)))