The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A272628 Primes p such that (p^2 + p + 1)/7 is prime. 1
 11, 23, 53, 179, 233, 317, 389, 401, 443, 599, 641, 683, 977, 1019, 1061, 1187, 1229, 1409, 1481, 1523, 1619, 1787, 1997, 2069, 2111, 2657, 2963, 3299, 3329, 3371, 3413, 3593, 3677, 3719, 4139, 4421, 4463, 5009, 5147, 5189, 5231, 5303, 5387, 5693 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Primes in A002641. LINKS Seiichi Manyama, Table of n, a(n) for n = 1..1000 EXAMPLE a(1) = 11 because (11^2+11+1)/7 = 19 is a prime. MATHEMATICA Select[Prime[Range[5000]], PrimeQ[(#^2 + # + 1) / 7] &] PROG (PARI) lista(nn) = {forprime(p=2, nn, if ((denominator(q=(p^2 + p + 1)/7) == 1) && isprime(q), print1(p, ", ")); ); } \\ Michel Marcus, May 05 2016 CROSSREFS Cf. A002641. Sequence in context: A066179 A217566 A278869 * A141093 A041236 A097485 Adjacent sequences:  A272625 A272626 A272627 * A272629 A272630 A272631 KEYWORD nonn AUTHOR Vincenzo Librandi, May 04 2016 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified September 19 15:09 EDT 2020. Contains 337178 sequences. (Running on oeis4.)