A086096 Semiprimes with a semiprime number of 1's in their binary representation.
15, 39, 46, 51, 57, 58, 77, 85, 86, 95, 106, 111, 119, 123, 141, 142, 159, 166, 169, 177, 178, 183, 187, 201, 202, 209, 215, 219, 221, 226, 235, 237, 249, 267, 278, 287, 291, 298, 303, 305, 323, 326, 329, 335, 365, 371, 377, 393, 394, 407, 411, 413, 417, 427
Offset: 1
Examples
The sixth semiprime = 15 = '1111' with four 1's, so 15 is a term.
Links
- Amiram Eldar, Table of n, a(n) for n = 1..10000
Programs
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Mathematica
binWt[n_] := DigitCount[n, 2, 1]; seqQ[n_] := PrimeOmega[n] == 2 && PrimeOmega[binWt[n]] == 2; Select[Range[500], seqQ] (* Amiram Eldar, Dec 14 2019 *) Select[Range[500],PrimeOmega[#]==PrimeOmega[DigitCount[#,2,1]]==2&] (* Harvey P. Dale, Feb 17 2025 *)