1,2

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

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

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

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

Cf. A001358, A014499.

Sequence in context: A281945 A163107 A275840 * A057748 A057747 A281965

Adjacent sequences: A178062 A178063 A178064 * A178066 A178067 A178068

nonn,base,easy

Juri-Stepan Gerasimov, May 18 2010

a(56) corrected by R. J. Mathar, May 23 2010

approved