

A036539


a(n) is the number of numbers k with 2^(n1) < 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
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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^(n1)+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



