A023578 - OEIS

%I #17 Feb 03 2022 14:23:00

%S 5,3,1,5,7,1,5,11,13,1,17,5,11,23,5,7,31,1,5,37,19,41,43,23,5,13,53,5,

%T 7,29,5,67,5,71,19,7,5,83,5,11,7,23,97,7,5,101,107,113,5,29,59,11,61,

%U 127,5,7,17,137,5,71,11,37,5,157,79,5,167,5,5,11,89,181,5,47,191

%N Least odd prime divisor of prime(n)+3, or 1 if prime(n)+3 is a power of 2.

%F a(n) = A078701(A113935(n)). - _Michel Marcus_, Aug 05 2021

%o (PARI) a(n) = my(p = prime(n)+3, v = p/(2^valuation(p, 2))) ; if (v == 1, 1, factor(v)[1, 1]); \\ _Michel Marcus_, Aug 05 2021

%o (Python)

%o from sympy import factorint, prime

%o def A023578(n): return min((p for p in factorint(prime(n)+3) if p > 2), default=1) # _Chai Wah Wu_, Feb 03 2022

%Y Cf. A023505, A078701, A113935.

%K nonn

%O 1,1

%A _Clark Kimberling_