A191401 k-almost primes which are digitally balanced in base 2 and have 2k digits in base 2, for some k >= 1.

2, 9, 10, 42, 44, 50, 52, 135, 150, 156, 184, 198, 204, 210, 225, 228, 232, 675, 684, 696, 728, 744, 752, 920, 944, 968, 976, 2484, 2544, 2646, 2673, 2744, 2772, 2835, 2904, 2928, 2992, 3132, 3150, 3192

Offset

1,1

Comments

The sequence contains all terms j of A031443 where A001222(j) = A070939(j)/2.

Links

Table of n, a(n) for n=1..40.

Example

10=A031443(3) is in the sequence because it has 2 ones and 2 zeros in binary, and is a semiprime (A001358).
50=A031443(12) is in the sequence because it has 3 ones and 3 zeros in binary and is a 3-almost prime (A014612).

Maple

isA031443 := proc(n) local d2 ; d2 := nops(convert(n, base, 2)) ; return( 2*wt(n) = d2 ) ; end proc ;
isA191401 := proc(n) local k ; if isA031443(n) then k := nops(convert(n, base, 2))/2 ; return( numtheory[bigomega](n) = k ) ; else false; end if; end proc:
for n from 1 to 3200 do if isA191401(n) then printf("%d, ", n) ; end if; end do: # R. J. Mathar, Jun 08 2011

Crossrefs

Cf. A031443.

Sequence in context: A179888 A073082 A300129 * A363223 A338997 A363951

Adjacent sequences: A191398 A191399 A191400 * A191402 A191403 A191404

Keyword

nonn,base,less

Author

Juri-Stepan Gerasimov, Jun 01 2011

Extensions

Corrected by R. J. Mathar, Jun 08 2011

Status

approved