A264822 Centered 15-gonal (or pentadecagonal) primes.

151, 421, 541, 991, 1171, 1801, 2851, 6091, 11701, 12301, 14851, 16921, 19891, 30241, 34171, 42751, 43891, 52291, 53551, 58741, 62791, 64171, 80341, 81901, 93241, 107101, 121921, 131671, 156601, 163171, 165391, 183691, 193201, 210421, 231001, 233641, 241651, 244351

Offset: 1

Author

Ilya Gutkovskiy, Nov 26 2015

Keywords

• nonn

Comments

Primes of the form (15*k^2 - 15*k + 2)/2.

All the terms in this sequence are congruent to 1 (mod 10). - K. D. Bajpai, Nov 29 2015

The associated k-values are 5, 8, 9, 12, 13, 16, 20, 29, 40, 41, 45, 48, 52, 64, 68, 76, 77, 84, 85, 89, ... - Danny Rorabaugh, Jan 18 2016

Links

• K. D. Bajpai, Table of n, a(n) for n = 1..10000
• OEIS Wiki, Figurate numbers
• Eric Weisstein's World of Mathematics, Centered Polygonal Number and Prime Number

Crossrefs

Cf. A000040, A069128.

Programs

Magma

[k: n in [1..10000] | IsPrime(k) where k is (15*n^2-15*n+2) div 2]; // K. D. Bajpai, Nov 29 2015

Maple

select(isprime, [seq((15*k^2 - 15*k + 2) / 2, k=0..1000)]); # K. D. Bajpai, Nov 29 2015

Mathematica

Select[Table[(15n^2 - 15n + 2) / 2, {n, 500}], PrimeQ] (* K. D. Bajpai, Nov 29 2015 *)

PARI

for(n=1, 1e3, if(isprime(k=(15*n^2-15*n+2)/2), print1(k,", "))) \\ Altug Alkan, Nov 26 2015