A178065 - OEIS

A178065

Number of 1's in binary representation of n-th semiprime.

1, 2, 2, 2, 3, 4, 3, 3, 3, 3, 2, 2, 3, 3, 4, 4, 3, 4, 5, 4, 4, 5, 2, 3, 3, 4, 3, 4, 4, 5, 5, 5, 5, 6, 4, 6, 5, 5, 6, 5, 5, 6, 2, 3, 3, 4, 4, 5, 3, 3, 5, 5, 6, 3, 4, 4, 4, 4, 6, 5, 6, 3, 4, 4, 5, 5, 5, 4, 5, 5, 6, 5, 5, 6, 6, 4, 6, 6, 7, 6, 7, 7, 3, 3, 3, 4, 3, 4, 6, 3, 4, 5, 4, 5, 5, 5, 6, 4, 5, 5, 7, 3, 4, 4, 5

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

Table of n, a(n) for n=1..105.

EXAMPLE

a(1)=1 because the first semiprime is 4 = 100_2.

a(2)=2 because the second semiprime is 6 = 110_2.

PROG

(PARI) lista(nn) = {for (n=2, nn, if (bigomega(n)==2, print1(norml2(binary(n)), ", ")); ); } \\ Michel Marcus, Jun 05 2013

CROSSREFS

Cf. A001358, A014499.