

A135772


Numbers having equal number of divisors and binary digits.


11



1, 2, 3, 4, 8, 10, 14, 15, 16, 32, 44, 45, 50, 52, 63, 64, 128, 130, 135, 136, 138, 152, 154, 165, 170, 174, 182, 184, 186, 189, 190, 195, 222, 230, 231, 232, 238, 246, 248, 250, 255, 256, 441, 484, 512, 567, 592, 656, 688, 752, 848, 891, 944, 976
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,2


LINKS

G. C. Greubel, Table of n, a(n) for n = 1..1000


EXAMPLE

a(1) = 1 since 1 has 1 divisor and 1 binary digit.
a(2), a(3) = 2, 3 since 2 = 10_2 and 3 = 11_2 have 2 divisors and 2 binary digits.
a(4) = 4 = 100_2 is the only number with 3 binary digits having 3 divisors.
8, 10, 14, 15 have 4 binary digits and 4 divisors.


MATHEMATICA

Select[Range[500], DivisorSigma[0, #] == IntegerLength[#, 2] &] (* G. C. Greubel, Nov 08 2016 *)


PROG

(PARI) for(d=1, 10, for(n=2^(d1), 2^d1, d==numdiv(n)&print1(n", ")))


CROSSREFS

Cf. A135773A135779, A095862.
Sequence in context: A061193 A180941 A190896 * A209064 A222264 A051783
Adjacent sequences: A135769 A135770 A135771 * A135773 A135774 A135775


KEYWORD

base,nonn


AUTHOR

M. F. Hasler, Nov 28 2007


STATUS

approved



