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A264845
Centered 20-gonal (or icosagonal) primes.
1
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
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
Sequence in context: A266134 A305019 A316683 * A340159 A142034 A338102
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Nov 26 2015
STATUS
approved