A264845 Centered 20-gonal (or icosagonal) primes.

61, 421, 1321, 3061, 4201, 4621, 5521, 7561, 12601, 14821, 15601, 18061, 19801, 28621, 35401, 42901, 44221, 52561, 55501, 74821, 76561, 81901, 87421, 97021, 109201, 111301, 115561, 117721, 131101, 135721, 150061, 189061, 217561, 235621, 251221, 270601, 273901

Offset

1,1

Comments

Primes of the form 10*k^2 - 10*k + 1.

Links

Table of n, a(n) for n=1..37.

OEIS Wiki, Figurate numbers

Eric Weisstein's World of Mathematics, Centered Polygonal Number

Eric Weisstein's World of Mathematics, Prime Number

Mathematica

Select[Table[10 n^2 - 10 n + 1, {n, 200}], PrimeQ] (* Vincenzo Librandi, Nov 27 2015 *)

Prog

(PARI) for(n=1, 1e3, if(isprime(k=10*n^2-10*n+1), print1(k, ", "))) \\ Altug Alkan, Nov 26 2015

Crossrefs

Cf. A000040, A069133.

Sequence in context: A266134 A305019 A316683 * A340159 A142034 A338102

Adjacent sequences: A264842 A264843 A264844 * A264846 A264847 A264848

Keyword

nonn

Author

Ilya Gutkovskiy, Nov 26 2015

Status

approved