cp's OEIS Frontend

A264822 Centered 15-gonal (or pentadecagonal) primes.

%I A264822 #25 Feb 16 2025 08:33:27
%S A264822 151,421,541,991,1171,1801,2851,6091,11701,12301,14851,16921,19891,
%T A264822 30241,34171,42751,43891,52291,53551,58741,62791,64171,80341,81901,
%U A264822 93241,107101,121921,131671,156601,163171,165391,183691,193201,210421,231001,233641,241651,244351
%N A264822 Centered 15-gonal (or pentadecagonal) primes.
%C A264822 Primes of the form (15*k^2 - 15*k + 2)/2.
%C A264822 All the terms in this sequence are congruent to 1 (mod 10). - _K. D. Bajpai_, Nov 29 2015
%C A264822 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
%H A264822 K. D. Bajpai, <a href="/A264822/b264822.txt">Table of n, a(n) for n = 1..10000</a>
%H A264822 OEIS Wiki, <a href="https://oeis.org/wiki/Figurate_numbers">Figurate numbers</a>
%H A264822 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/CenteredPolygonalNumber.html">Centered Polygonal Number</a> and <a href="https://mathworld.wolfram.com/PrimeNumber.html">Prime Number</a>
%p A264822 select(isprime, [seq((15*k^2 - 15*k + 2) / 2, k=0..1000)]); # _K. D. Bajpai_, Nov 29 2015
%t A264822 Select[Table[(15n^2 - 15n + 2) / 2, {n, 500}], PrimeQ] (* _K. D. Bajpai_, Nov 29 2015 *)
%o A264822 (PARI) for(n=1, 1e3, if(isprime(k=(15*n^2-15*n+2)/2), print1(k,", "))) \\ _Altug Alkan_, Nov 26 2015
%o A264822 (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
%Y A264822 Cf. A000040, A069128.
%K A264822 nonn
%O A264822 1,1
%A A264822 _Ilya Gutkovskiy_, Nov 26 2015