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%I #28 Feb 23 2024 10:46:35
%S 1,1,0,1,0,1,0,0,0,1,0,0,0,1,0,1,0,0,0,1,0,0,0,1,0,1,0,0,0,0,0,0,0,0,
%T 0,1,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,1,0,0,0,0,0,0,0,0,0,1,0,0,
%U 0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,1,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,1,0,0,0,1
%N a(n) = 1 if n^2+1 is prime, 0 otherwise.
%C It is conjectured that n^2+1 is prime infinitely often.
%H Antti Karttunen, <a href="/A295405/b295405.txt">Table of n, a(n) for n = 1..100000</a> (first 10000 terms from Simon Plouffe)
%H <a href="/index/Ch#char_fns">Index entries for characteristic functions</a>
%F a(n) = A010051(A002522(n)). - _Robert Israel_, Nov 22 2017
%e With n=1, a(1) = 2, n=2, a(2) = 5, a(3) = 0 since 10 is not prime.
%p seq(`if`(isprime(n^2+1),1,0),n=1..100); # _Robert Israel_, Nov 22 2017
%t Boole[PrimeQ[Range[150]^2+1]] (* _Paolo Xausa_, Feb 23 2024 *)
%o (PARI) a(n)=isprime(n^2+1)
%Y Characteristic function of A005574.
%Y Cf. A002496, A002522, A010051.
%Y Cf. also A355449.
%K nonn
%O 1
%A _Simon Plouffe_, Nov 22 2017
%E Data section extended up to term a(120) by _Antti Karttunen_, Jul 12 2022
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