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A100587 Number of non-empty subsets of divisors of n. 1
1, 3, 3, 7, 3, 15, 3, 15, 7, 15, 3, 63, 3, 15, 15, 31, 3, 63, 3, 63, 15, 15, 3, 255, 7, 15, 15, 63, 3, 255, 3, 63, 15, 15, 15, 511, 3, 15, 15, 255, 3, 255, 3, 63, 63, 15, 3, 1023, 7, 63, 15, 63, 3, 255, 15, 255, 15, 15, 3, 4095, 3, 15, 63, 127, 15, 255, 3, 63, 15, 255, 3, 4095, 3 (list; graph; refs; listen; history; internal format)
OFFSET

1,2

FORMULA

a[n]=-1+2^tau[n], tau[n]=DivisorSigma[0, n]=A000005[n]

EXAMPLE

For all prime numbers p, a[p]=3, since those subsets are {{1,p},{1},{p}}.

CROSSREFS

Cf. A100371, A000005, A066781.

Sequence in context: A119347 A062402 A156838 * A187419 A099282 A002937

Adjacent sequences:  A100584 A100585 A100586 * A100588 A100589 A100590

KEYWORD

nonn

AUTHOR

Labos E. (labos(AT)ana.sote.hu), Dec 01 2004

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Last modified February 14 23:16 EST 2012. Contains 205687 sequences.