A378159 The least prime dividing A000255(n); a(1) = 1.

1, 3, 11, 53, 3, 13, 11, 3, 1468457, 11, 3, 1373, 34361893981, 3, 17713, 2130617, 3, 11, 13, 3, 11, 617, 3, 37, 11, 3, 179, 14633, 3, 76463, 97, 3, 337, 1049, 3, 11, 7237598635049, 3, 67, 11, 3, 22742406079421034331584846001936724930824184898296683, 11, 3, 13

Offset: 1

Author

Amiram Eldar, Nov 18 2024

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..137

Crossrefs

Cf. A000255, A020639, A301423, A378157.

Programs

Mathematica

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

PARI

lpf(n) = if(n == 1, 1, factor(n)[1,1]);
lista(nmax) = {my(s = 1); for(n = 1, nmax, s = (n * (n+2) * s + (-1)^n)/(n+1); print1(lpf(s), ", "));}

Formula

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

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

a(3*n-1) = 3.