A166948 The count of smallest prime factors in n-th composite.

2, 1, 3, 2, 1, 2, 1, 1, 4, 1, 2, 1, 1, 3, 2, 1, 3, 2, 1, 5, 1, 1, 1, 2, 1, 1, 3, 1, 2, 2, 1, 4, 2, 1, 1, 2, 1, 1, 3, 1, 1, 2, 1, 2, 6, 1, 1, 2, 1, 1, 3, 1, 1, 2, 1, 1, 4, 4, 1, 2, 1, 1, 1, 3, 1, 1, 2, 1, 1, 1, 5, 1, 2, 2, 1, 3, 1, 1, 2, 1, 1, 4, 1, 1, 2, 2, 1, 1, 3, 2, 1, 1, 2, 3, 1, 7, 1, 1, 2, 1, 1, 3, 3, 1, 2

Offset

1,1

Links

Table of n, a(n) for n=1..105.

Example

a(1)=2 (4 = 2*2);
a(2)=1 (6 = 2*3);
a(3)=3 (8 = 2*2*2);
a(4)=2 (9 = 3*3).

Maple

A020639 := proc(n) numtheory[factorset](n) ; min(op(%)) ; end proc:
A166948 := proc(n) c := A002808(n) ; smpr := A020639(c) ; for p in ifactors(c)[2] do if op(1, p) = smpr then return op(2, p) ; end if; end do: end proc:
seq(A166948(n), n=1..120) ; # R. J. Mathar, May 21 2010

Mathematica

FactorInteger[#][[1, 2]]&/@Select[Range[200], CompositeQ] (* Harvey P. Dale, Apr 20 2022 *)

Crossrefs

Cf. A002808, A020639.

Sequence in context: A103484 A016444 A280831 * A325532 A180075 A193865

Adjacent sequences: A166945 A166946 A166947 * A166949 A166950 A166951

Keyword

nonn

Author

Juri-Stepan Gerasimov, Oct 25 2009

Extensions

Entries checked by R. J. Mathar, May 21 2010

Status

approved