%I #8 Jun 25 2024 13:13:09
%S 0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,
%T 1,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,
%U 0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0
%N a(n) = 1 if n is a nonprime of the form 4*k + 3, otherwise 0.
%H Antti Karttunen, <a href="/A373979/b373979.txt">Table of n, a(n) for n = 1..100000</a>
%H <a href="/index/Ch#char_fns">Index entries for characteristic functions</a>
%t a[n_]:=Boole[!PrimeQ[n]&&Mod[n,4]==3]; Array[a,125](* _Stefano Spezia_, Jun 25 2024 *)
%o (PARI) A373979(n) = (!isprime(n) && 3==(n%4));
%Y Characteristic function of A091236.
%Y Cf. also A079261, A373978.
%K nonn
%O 1
%A _Antti Karttunen_, Jun 25 2024