A360128 - OEIS

%I #10 Feb 21 2023 17:19:07

%S 1,1,1,1,1,0,1,1,1,1,1,0,1,1,1,1,1,0,1,0,1,1,1,0,1,1,1,1,1,0,1,1,1,1,

%T 1,0,1,1,1,0,1,0,1,1,1,1,1,0,1,1,1,1,1,0,1,0,1,1,1,0,1,1,1,1,1,0,1,1,

%U 1,1,1,0,1,1,1,1,1,0,1,0,1,1,1,0,1,1,1,1,1,0,1,1,1,1,1,0,1,1,1,0,1,0,1,1,1,1,1,0,1,0,1,0,1,0,1,1,1,1,1,0,1

%N a(n) = 1 if there are no divisors d>1 of n such that also d+1 is a divisor of n, otherwise 0.

%H Antti Karttunen, <a href="/A360128/b360128.txt">Table of n, a(n) for n = 1..100000</a>

%H <a href="/index/Ch#char_fns">Index entries for characteristic functions</a>

%F a(n) = [A088722(n) == 0], where [ ] is the Iverson bracket.

%F a(n) = [A129308(n) < 2] = [A328457(n) < 2].

%o (PARI) A360128(n) = !sumdiv(n,d,(d>1)&&!(n%(d+1)));

%Y Characteristic function of A088725.

%Y Cf. A088722, A129308, A328457, A360129.

%K nonn

%O 1

%A _Antti Karttunen_, Feb 20 2023