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