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A085955
Composites such that the number of 1's in their binary expansion is equal to the number of 1's in the binary expansion of the sum of their prime factors (counting repetition).
1
4, 6, 9, 16, 20, 22, 24, 28, 36, 38, 49, 56, 65, 69, 70, 72, 84, 86, 92, 100, 104, 105, 118, 130, 132, 133, 134, 138, 148, 150, 152, 153, 162, 166, 176, 180, 184, 208, 209, 212, 214, 216, 256, 258, 259, 261, 262, 264, 266, 267, 278, 284, 320, 325, 326, 329, 345
OFFSET
1,1
LINKS
EXAMPLE
a(42) = 216 because 216 = '11011000' and sopfr(216) = 15 = '1111'; both have four 1's.
MATHEMATICA
binWt[n_] := DigitCount[n, 2, 1]; seqQ[n_] := CompositeQ[n] && binWt[n] == binWt[Plus @@ Times @@@ FactorInteger[n]]; Select[Range[350], seqQ] (* Amiram Eldar, Dec 14 2019 *)
CROSSREFS
KEYWORD
easy,nonn,base
AUTHOR
Jason Earls, Aug 17 2003
STATUS
approved