A089992 Second prime divisor of numbers that are not powers of primes (A024619).

3, 5, 3, 7, 5, 3, 5, 7, 11, 3, 13, 7, 3, 11, 17, 7, 3, 19, 13, 5, 3, 11, 5, 23, 3, 5, 17, 13, 3, 11, 7, 19, 29, 3, 31, 7, 13, 3, 17, 23, 5, 3, 37, 5, 19, 11, 3, 5, 41, 3, 17, 43, 29, 11, 3, 13, 23, 31, 47, 19, 3, 7, 11, 5, 3, 13, 5, 53, 3, 5, 37, 7, 3, 23, 29, 13, 59, 17, 3, 61, 41, 31, 3, 43

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Formula

a(n) = A119288(A024619(n)). - Amiram Eldar, Apr 12 2021

Mathematica

Select[Table[If[Length[(f = FactorInteger[n])] > 1, f[[2, 1]], 1], {n, 1, 150}], # > 1 &]

Prog

(PARI) f(n) = a=factor(n); v=a[, 1]; ln=length(v); if(ln>1, return(v[2]));
g(m) = for(x=2, m, if(f(x)>0, print1(f(x)", ")));

Crossrefs

Cf. A024619, A119288, A089993.

Sequence in context: A029604 A079602 A075572 * A074593 A144294 A255313

Adjacent sequences: A089989 A089990 A089991 * A089993 A089994 A089995

Keyword

nonn

Author

Cino Hilliard, Jan 14 2004

Extensions

Offset corrected by Amiram Eldar, Apr 12 2021

Status

approved