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A135591 a(n) is number of earlier terms equal to number of proper divisors of n. 2
1, 1, 2, 1, 3, 1, 4, 1, 1, 1, 7, 0, 7, 1, 1, 1, 10, 0, 10, 0, 1, 1, 12, 2, 2, 1, 1, 0, 14, 2, 14, 0, 1, 1, 1, 0, 17, 1, 1, 2, 19, 2, 19, 0, 0, 1, 20, 0, 6, 0, 1, 0, 21, 2, 1, 2, 1, 1, 24, 0, 24, 1, 0, 1, 1, 2, 27, 0, 1, 2, 28, 0, 28, 1, 0, 0, 1, 2, 30, 0, 1, 1, 32, 0, 1, 1, 1, 2, 35, 0, 1, 0, 1, 1, 1, 0, 39 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Similar to A125087, but instead of exponents, we use number of proper divisors.

LINKS

Katarzyna Matylla, Table of n, a(n) for n = 1..1000

EXAMPLE

a(12)=0 because 12 has 5 proper divisors (1, 2, 3, 4 and 6) and there is no 5 in a(1), a(2), ..., a(11).

PROG

Maxima: max:1000; f:makelist(0, i, 1, max); apr:makelist(0, i, 0, max); f[1]:1; apr[2]:1; for n:2 through max do block(f[n]:apr[divsum(n, 0)], apr[f[n]+1]:apr[f[n]+1]+1);

CROSSREFS

Cf. A125087.

Sequence in context: A325252 A243334 A234809 * A114897 A210954 A195843

Adjacent sequences:  A135588 A135589 A135590 * A135592 A135593 A135594

KEYWORD

nonn

AUTHOR

Katarzyna Matylla, Feb 25 2008

STATUS

approved

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Last modified January 21 13:55 EST 2020. Contains 331113 sequences. (Running on oeis4.)