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A078662 Number of balanced numbers <= 2^n. 1
1, 2, 3, 4, 7, 8, 11, 14, 19, 24, 33, 39, 54, 69, 91, 122, 160, 206, 270, 346, 451, 575, 737, 962, 1260, 1635, 2110, 2712, 3491, 4564, 5942, 7773, 10195, 13357, 17441, 22920, 30093, 39658 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..37.

EXAMPLE

There are nine balanced numbers between 512 and 1024: {570,594,616,630,714,744,812,840,910}, so a(10) = 9+a(9) = 33.

MATHEMATICA

k = 1; c = 0; Do[ While[k <= 2^n, If[ IntegerQ[ DivisorSigma[1, k]/EulerPhi[k]], c++ ]; k++ ]; Print[c], {n, 0, 24}]

CROSSREFS

Cf. A020492, A078555.

Sequence in context: A225229 A239389 A256219 * A050048 A122456 A186243

Adjacent sequences:  A078659 A078660 A078661 * A078663 A078664 A078665

KEYWORD

nonn

AUTHOR

Labos Elemer, Dec 06 2002

EXTENSIONS

More terms from Robert G. Wilson v, Dec 14 2002

a(25)-a(37) from Donovan Johnson, Mar 03 2013

STATUS

approved

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Last modified June 1 19:32 EDT 2020. Contains 334762 sequences. (Running on oeis4.)