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A126132 a(n) = number of k's, 1<=k<=n, where d(k) is equal to any divisor of n, where d(k) is the number of positive divisors of k. 1
1, 2, 1, 3, 1, 5, 1, 7, 3, 5, 1, 12, 1, 7, 3, 12, 1, 12, 1, 15, 3, 9, 1, 23, 2, 10, 4, 19, 1, 19, 1, 23, 4, 12, 2, 33, 1, 13, 4, 31, 1, 22, 1, 29, 6, 15, 1, 45, 1, 18, 5, 32, 1, 31, 2, 40, 5, 17, 1, 53, 1, 19, 6, 45, 2, 33, 1, 41, 5, 23, 1, 69, 1, 22, 6, 45, 2, 39, 1, 59, 6, 23, 1, 70, 3, 24, 5 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..87.

EXAMPLE

The number of divisors of the integers 1 through 10 form the sequence 1,2,2,3,2, 4,2,4,3,4. The divisors of 10 are 1,2,5,10. The terms of the sequence of the first ten d(k)'s which equal any divisor of 10 are the five terms 1,2,2,2,2. So a(10) = 5.

MATHEMATICA

f[n_] := Length@Select[Table[Length@Divisors[k], {k, n}], MemberQ[Divisors[n], # ] &]; Table[f[n], {n, 87}] (* Ray Chandler, Dec 20 2006 *)

CROSSREFS

Cf. A126131.

Sequence in context: A101809 A127203 A227288 * A129982 A052552 A147000

Adjacent sequences:  A126129 A126130 A126131 * A126133 A126134 A126135

KEYWORD

nonn

AUTHOR

Leroy Quet, Dec 18 2006

EXTENSIONS

Extended by Ray Chandler, Dec 20 2006

STATUS

approved

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Last modified January 24 10:42 EST 2020. Contains 331193 sequences. (Running on oeis4.)