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A036539 a(n) is the number of numbers k with 2^(n-1) < k <= 2^n having a number of divisors that is a power of 2. 1
1, 1, 4, 5, 11, 22, 44, 89, 178, 351, 702, 1413, 2817, 5634, 11273, 22542, 45077, 90150, 180322, 360621, 721233, 1442482, 2884968, 5769917, 11539863, 23079674, 46159310, 92318616, 184637146, 369274400, 738548882, 1477097703, 2954195153, 5908390134, 11816780283 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..35.

EXAMPLE

a(5) = 11: The following 11 numbers have number of divisors which are powers of 2: 17,19,21,22,23,24,26,27,29,30,31 with 2,2,4,4,2,8,4,4,2,8,2 divisors respectively.

PROG

(PARI) a(n)=sum(k=2^(n-1)+1, 2^n, my(d=numdiv(k)); (d/(1<<valuation(d, 2)))==1 ); \\ Joerg Arndt, Feb 27 2017

CROSSREFS

Cf. A037992.

Sequence in context: A185507 A000286 A227620 * A279710 A303956 A000769

Adjacent sequences:  A036536 A036537 A036538 * A036540 A036541 A036542

KEYWORD

nonn

AUTHOR

Labos Elemer

EXTENSIONS

Name clarified and more terms from Joerg Arndt, Feb 27 2017

a(25)-a(28) from Jon E. Schoenfield, Jul 31 2018

a(29)-a(35) from Jon E. Schoenfield, Aug 04 2018

STATUS

approved

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Last modified October 14 01:36 EDT 2019. Contains 327994 sequences. (Running on oeis4.)