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A100008 Number of unitary divisors of 2n. +0
1
2, 2, 4, 2, 4, 4, 4, 2, 4, 4, 4, 4, 4, 4, 8, 2, 4, 4, 4, 4, 8, 4, 4, 4, 4, 4, 4, 4, 4, 8, 4, 2, 8, 4, 8, 4, 4, 4, 8, 4, 4, 8, 4, 4, 8, 4, 4, 4, 4, 4, 8, 4, 4, 4, 8, 4, 8, 4, 4, 8, 4, 4, 8, 2, 8, 8, 4, 4, 8, 8, 4, 4, 4, 4, 8, 4, 8, 8, 4, 4, 4, 4, 4, 8, 8, 4, 8, 4, 4, 8, 8, 4, 8, 4, 8, 4, 4, 4, 8, 4, 4, 8, 4, 4, 16 (list; graph; listen)
OFFSET

1,1

COMMENT

b(n) = a(n)/a(1) is multiplicative with b(2^e) = 1, b(p^e) = 2 otherwise. David W. Wilson (davidwwilson(AT)comcast.net) Jun 12, 2005.

EXAMPLE

a(6)=4 because among the six divisors of 12 only 1,3,4 and 12 are unitary.

MAPLE

with(numtheory): for n from 1 to 120 do printf(`%d, `, 2^nops(ifactors(2*n)[2])) od: (Deutsch)

CROSSREFS

Bisection of A034444.

Sequence in context: A152858 A091248 A082991 this_sequence A102763 A054844 A057936

Adjacent sequences: A100005 A100006 A100007 this_sequence A100009 A100010 A100011

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane (njas(AT)research.att.com), Nov 20 2004

EXTENSIONS

More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Dec 24 2004

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Last modified December 15 00:47 EST 2009. Contains 170825 sequences.


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