A074592 Smallest prime factors of numbers that are not prime powers.

2, 2, 2, 2, 3, 2, 2, 3, 2, 2, 2, 2, 2, 3, 2, 5, 2, 2, 3, 2, 2, 2, 3, 2, 2, 2, 3, 2, 2, 5, 2, 3, 2, 2, 2, 3, 5, 2, 2, 3, 2, 2, 2, 3, 2, 7, 2, 2, 2, 2, 5, 2, 3, 2, 2, 7, 2, 3, 2, 5, 2, 2, 3, 2, 2, 2, 3, 2, 2, 2, 3, 2, 2, 5, 2, 3, 2, 7, 2, 2, 3, 2, 2, 3, 2, 2, 7, 2, 3, 2, 2, 2, 3, 2, 11, 2, 5, 2, 3, 2, 2, 2, 3, 2

Offset

1,1

Links

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

Formula

a(n) = A020639(A024619(n)).

a(n) > 2 iff n+1 and n+2 are prime powers (A006549).

Mathematica

s[n_] := Module[{f = FactorInteger[n]}, If[Length[f] > 1, f[[1, 1]], Nothing]]; Array[s, 200] (* Amiram Eldar, Oct 10 2024 *)

Crossrefs

Cf. A006549, A020639, A024619, A074593, A074594, A074595.

Sequence in context: A327163 A324538 A305976 * A089993 A220431 A351284

Adjacent sequences: A074589 A074590 A074591 * A074593 A074594 A074595

Keyword

nonn

Author

Reinhard Zumkeller, Aug 25 2002

Status

approved