This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A027864 #44 Jul 22 2025 15:50:14
%S A027864 5,29,149,509,677,1877,3677,8429,9749,11909,13469,17789,22709,27077,
%T A027864 28229,45389,46877,53069,70229,72077,81677,100469,102677,114077,
%U A027864 128549,141269,154589,180077,192029,195077,207509,223589,230189,261077,312989,340709
%N A027864 Primes of the form k^2 + (k+1)^2 + (k+2)^2 = 3*(k+1)^2+2.
%C A027864 Same as A257163 without its first term. - _Jonathan Sondow_, Oct 24 2015
%C A027864 The domain of k is not explicit. If the domain is all integers then the sequence A257163 is produced. In this sequence domain is all nonnegative integers. - _Michael Somos_, Oct 24 2015
%D A027864 James J. Tattersall, Elementary Number Theory in Nine Chapters, Cambridge University Press, 1999, page 247.
%H A027864 Harvey P. Dale, <a href="/A027864/b027864.txt">Table of n, a(n) for n = 1..1000</a>
%t A027864 Select[Table[3n^2+6n+5,{n,0,400}],PrimeQ] (* _Harvey P. Dale_, Oct 22 2016 *)
%t A027864 Select[Table[Total[Range[n,n+2]^2],{n,0,500}],PrimeQ] (* _Harvey P. Dale_, May 23 2021 *)
%o A027864 (PARI) select(isprime, vector(100,n,3*n^2+2)) \\ _Charles R Greathouse IV_, Apr 17 2015
%o A027864 (Python)
%o A027864 from sympy import isprime
%o A027864 print(list(filter(isprime, (3*k**2+6*k+5 for k in range(350))))) # _Michael S. Branicky_, May 29 2021
%Y A027864 Cf. A027574, A257163.
%K A027864 nonn,easy
%O A027864 1,1
%A A027864 _Patrick De Geest_
%E A027864 More terms from _Claudio Meller_, Jun 25 2009