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 A093641 Numbers of form 2^i * prime(j), i>=0, j>0, together with 1. 55
 1, 2, 3, 4, 5, 6, 7, 8, 10, 11, 12, 13, 14, 16, 17, 19, 20, 22, 23, 24, 26, 28, 29, 31, 32, 34, 37, 38, 40, 41, 43, 44, 46, 47, 48, 52, 53, 56, 58, 59, 61, 62, 64, 67, 68, 71, 73, 74, 76, 79, 80, 82, 83, 86, 88, 89, 92, 94, 96, 97, 101, 103, 104, 106, 107, 109, 112 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(n) is either 1, prime, or of form 2a(m), minfinity). - Vladimir Shevelev, Feb 06 2014 EXAMPLE 55 is not a member, as 5*11 is not of the form 2^i * prime. MATHEMATICA hookQ[n_]:=MatchQ[DeleteCases[FactorInteger[n], {2, _}], {}|{{_, 1}}]; Select[Range[100], hookQ] (* Gus Wiseman, Sep 15 2018 *) PROG (PARI) upTo(lim)=my(v=List([1])); for(e=0, log(lim)\log(2), forprime(p=2, lim>>e, listput(v, p<

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Last modified November 26 17:17 EST 2020. Contains 338641 sequences. (Running on oeis4.)