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 A055755 #9 Jul 02 2025 16:01:59
%S A055755 3,42,45,102,132,153,237,297,375,468,570,990,2085,2478,2712,3240,4743,
%T A055755 5382,5517,6828,7962,8970,8982,9033,9570,9612,9747,9813,10692,12363,
%U A055755 12453,12468,12750,13902,14763,14925,15750,16365,17118,17688,19527
%N A055755 4n^2+1, 2n^2+1, 2n^2-1 are all prime.
%H A055755 Peter J. C. Moses, <a href="/A055755/b055755.txt">Table of n, a(n) for n = 1..10000</a>
%e A055755 42 is included because 4*42^2+1, 2*42^2+1, 2*42^2-1 are all prime numbers.
%p A055755 with(numtheory): for n from 1 to 50000 do if isprime(4*n^2+1) and isprime(2*n^2+1) and isprime(2*n^2-1) then printf(`%d,`,n) fi: od:
%t A055755 a={};Do[If[PrimeQ[4n^2+1] && PrimeQ[2n^2+1] && PrimeQ[2n^2-1], AppendTo[a,n]], {n,10000}]; a (* _Peter J. C. Moses_, Apr 02 2013 *)
%Y A055755 Cf. A001912.
%K A055755 easy,nonn
%O A055755 1,1
%A A055755 _Harvey P. Dale_, Jul 12 2000
%E A055755 More terms from _James Sellers_, Jul 13 2000