OFFSET
1,1
EXAMPLE
132 has the prime factorization 2^2 * 3^1 * 11^1. This has 2 exponents each equal to 1. 132 in binary is 10000100, which has two 1's. Since the number of exponents in the prime factorization equals the number of 1's in the binary representation, then 132 is included in the sequence.
MAPLE
A000120 := proc(n) add(i, i=convert(n, base, 2)) ; end: A056169 := proc(n) a :=0 ; for p in ifactors(n)[2] do if op(2, p) = 1 then a := a+1 ; fi; od: RETURN(a) ; end: isA145541 := proc(n) RETURN( A000120(n) = A056169(n)) ; end: for n from 1 to 3000 do if isA145541(n) then printf("%d, ", n) ; fi; od: # R. J. Mathar, Oct 16 2008
MATHEMATICA
Select[Range[2, 2100], Length[Select[FactorInteger[#], #[[2]]==1&]] == DigitCount[ #, 2, 1]&] (* Harvey P. Dale, Apr 30 2014 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Leroy Quet, Oct 12 2008
EXTENSIONS
Extended by R. J. Mathar, Oct 16 2008
STATUS
approved