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 A072902 #28 Jun 24 2022 04:34:20
%S A072902 1,8,12,21,24,28,33,40,44,56,57,60,65,69,76,77,85,88,92,93,104,105,
%T A072902 120,124,129,133,136,140,141,145,152,156,161,165,168,172,177,184,185,
%U A072902 188,201,204,205,209,213,217,220,221,232,236,237,248,249,253,264,265,268
%N A072902 Nonprime numbers m such that the discriminant of the quadratic field Q(sqrt(m)) equals m.
%C A072902 A subset of the nonprime numbers (A018252).
%C A072902 Positive fundamental discriminants (A003658) that are not Pythagorean primes (A002144). - _Paul Muljadi_, Mar 30 2008
%H A072902 Amiram Eldar, <a href="/A072902/b072902.txt">Table of n, a(n) for n = 1..10000</a>
%F A072902 a(n) appears to be asymptotic to C*n with C = 3.91... .
%t A072902 FundamentalDiscriminantQ[d_] := Module[{m, mod = Mod[d, 4]}, If[mod > 1, Return[False]]; If[mod == 1, Return[ SquareFreeQ[d] && d != 1]]; m = d/4; Return[ SquareFreeQ[m] && Mod[m, 4] > 1]]; Join[{1}, Select[ Range[270], !PrimeQ[#] && FundamentalDiscriminantQ[#]& ]] (* _Jean-François Alcover_, Jun 05 2012, after _Eric W. Weisstein_ *)
%o A072902 (PARI) isok(m) = !isprime(m) && (quaddisc(m) == m); \\ _Michel Marcus_, Feb 18 2021
%Y A072902 Cf. A037449.
%Y A072902 Cf. A002144, A018252, A003658.
%K A072902 easy,nonn
%O A072902 1,2
%A A072902 _Benoit Cloitre_, Aug 10 2002