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A112659 a(1) = 1. For n >= 2, a(n) = number of earlier terms of the sequence which are divisible by a different number of distinct primes than n. 0
1, 1, 2, 2, 2, 5, 2, 2, 2, 9, 2, 11, 2, 13, 14, 3, 3, 16, 3, 18, 18, 18, 6, 18, 8, 19, 8, 21, 9, 29, 9, 9, 25, 26, 26, 26, 12, 26, 26, 26, 16, 41, 16, 29, 30, 31, 17, 33, 18, 33, 33, 33, 22, 33, 33, 33, 33, 33, 28, 58, 30, 34, 34, 33, 34, 63, 36, 34, 34 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..69.

EXAMPLE

Among the 15 earliest terms of the sequence there are 3 terms not divisible by exactly one distinct prime, as 16 is. (These 3 terms are 1, 1 {both divisible by 0 primes} and 14 {divisible by 2 distinct primes}.) So a(16) = 3.

MATHEMATICA

a = {1}; For[n = 2, n < 70, n++, c = 0; For[j = 1, j < Length[a] + 1, j++, If[Not[Length[FactorInteger[a[[j]]]] == Length[FactorInteger[n]]], c++ ]]; AppendTo[a, c]]; a (* Stefan Steinerberger, Nov 21 2007 *)

CROSSREFS

Cf. A001221.

Sequence in context: A275887 A121358 A271321 * A115281 A130155 A113516

Adjacent sequences:  A112656 A112657 A112658 * A112660 A112661 A112662

KEYWORD

nonn

AUTHOR

Leroy Quet, Dec 28 2005

EXTENSIONS

More terms from Stefan Steinerberger, Nov 21 2007

STATUS

approved

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Last modified June 17 21:47 EDT 2019. Contains 324200 sequences. (Running on oeis4.)