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

Author

Ilya Gutkovskiy, Nov 26 2015

Keywords

• nonn

Comments

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

Links

• OEIS Wiki, Figurate numbers
• Eric Weisstein's World of Mathematics, Centered Polygonal Number
• Eric Weisstein's World of Mathematics, Prime Number

Crossrefs

Cf. A000040, A069133.

Programs

Mathematica

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

PARI

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