A264825 - OEIS

A264825

Centered 18-gonal (or octadecagonal) primes.

19, 109, 181, 271, 379, 811, 991, 2161, 3079, 4159, 4969, 5851, 7309, 8929, 10099, 10711, 13339, 17029, 21169, 22051, 23869, 25759, 26731, 28729, 32941, 34039, 37441, 38611, 39799, 48619, 58321, 59779, 67339, 70489, 72091, 89101, 90901, 102079, 109891, 117991, 122149

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

Primes of the form 9*k^2 - 9*k + 1.

LINKS

Table of n, a(n) for n=1..41.

OEIS Wiki, Figurate numbers

Eric Weisstein's World of Mathematics, Centered Polygonal Number

Eric Weisstein's World of Mathematics, Prime Number

PROG

(PARI) for(n=1, 1e3, if(isprime(k=9*n^2-9*n+1), print1(k, ", "))) \\ Altug Alkan, Nov 26 2015