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 A121944 #4 Oct 24 2022 00:47:16
%S A121944 65,145,325,485,785,901,1025,1157,1445,1765,1937,2117,2305,2501,2705,
%T A121944 3365,3601,3845,4097,4625,4901,5185,5777,6085,6401,6725,7397,7745,
%U A121944 8465,9217,9605,10001,10405,10817,11237,11665,12545,12997,13925,14885,16385
%N A121944 Composite number of the form 4n^2+1.
%F A121944 a(n) ~ 4n^2 + O(n^2/log n). - _Charles R Greathouse IV_, Oct 24 2022
%t A121944 Select[Table[4n^2 + 1, {n, 70}], ! PrimeQ[ # ] &]
%Y A121944 a(n) are elements of A053755 = 4*n^2 + 1, beside 1 that are not prime, that is they do not lie in A002496 = Primes of form n^2 + 1.
%K A121944 nonn,easy
%O A121944 1,1
%A A121944 _Tanya Khovanova_, Sep 03 2006