A378159 - OEIS

%I #8 Nov 19 2024 00:59:13

%S 1,3,11,53,3,13,11,3,1468457,11,3,1373,34361893981,3,17713,2130617,3,

%T 11,13,3,11,617,3,37,11,3,179,14633,3,76463,97,3,337,1049,3,11,

%U 7237598635049,3,67,11,3,22742406079421034331584846001936724930824184898296683,11,3,13

%N The least prime dividing A000255(n); a(1) = 1.

%H Amiram Eldar, <a href="/A378159/b378159.txt">Table of n, a(n) for n = 1..137</a>

%F a(n) = A020639(A000255(n)).

%F a(n) = A000255(n) if and only if n+2 is a term of A301423.

%F a(3*n-1) = 3.

%t FactorInteger[#][[1, 1]] & /@ Table[Subfactorial[n + 2]/(n + 1), {n, 1, 44}]

%o (PARI) lpf(n) = if(n == 1, 1, factor(n)[1,1]);

%o lista(nmax) = {my(s = 1); for(n = 1, nmax, s = (n * (n+2) * s + (-1)^n)/(n+1); print1(lpf(s), ", "));}

%Y Cf. A000255, A020639, A301423, A378157.

%K nonn

%O 1,2

%A _Amiram Eldar_, Nov 18 2024