A285789 Primes equal to a pentagonal number plus 1.

2, 13, 23, 71, 211, 331, 853, 1163, 1427, 2381, 2753, 3433, 3877, 5923, 6113, 6701, 7741, 8627, 9323, 11311, 12377, 14653, 14951, 17443, 18427, 23003, 27271, 31033, 32341, 32783, 34127, 38321, 43777, 52361, 55201, 56941, 57527, 62323, 64171, 64793, 69877

Offset: 1

Author

Colin Barker, Apr 26 2017

Keywords

• nonn

Links

• Colin Barker, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A000040, A000326, A002496, A055469, A285790, A285791, A285792.

Programs

Mathematica

Select[PolygonalNumber[5,Range[300]]+1,PrimeQ] (* Harvey P. Dale, Dec 04 2024 *)

PARI

pg(m, n) = (n^2*(m-2)-n*(m-4))/2 \\ n-th m-gonal number
maxk=300; L=List(); for(k=1, maxk, if(isprime(p=pg(5, k) + 1), listput(L, p))); Vec(L)