A276809 Least prime p such that (p^2-1)/24 is divisible by prime(n) or 0 if no such prime exists.

7, 17, 11, 13, 23, 53, 67, 37, 47, 59, 61, 73, 83, 173, 281, 107, 353, 367, 269, 283, 293, 157, 167, 179, 193, 607, 617, 641, 653, 227, 509, 263, 547, 277, 1193, 907, 313, 653, 1669, 347, 359, 1087, 383, 773, 787, 397, 421, 1783, 907, 457, 467, 479, 1447, 503, 1543

Offset: 1

Author

Michel Marcus, Sep 18 2016

Keywords

• nonn

Comments

Sequence motivated by a comment in A024702: "The set of prime factors of a(n), however, appears to include all primes".

Examples

			a(1) = 7 because 7 is the least prime p such that (p^2-1)/24, which is 2, is divisible by 2=prime(1).
a(2) = 17 because 17 is the least prime p such that (p^2-1)/24, which is 12, is divisible by 3=prime(2).
a(3) = 11 because 11 is the least prime p such that (p^2-1)/24, which is 5, is divisible by 5=prime(3).
		

Links

• Seiichi Manyama, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A024702.

Programs

PARI

a(n) = {p = prime(n); q = prime(3); while (! vecsearch(factor((q^2 - 1)/24)[,1], p), q = nextprime(q+1)); q;}