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 A192734 Smallest number having binary weight of 3 and n distinct prime factors 1
 7, 21, 273, 16401, 1048593, 4295032833, 1099512676353, 9007199256838145, 302231455185132270387201, 1208944266358702884257793, 1329227995784915872903807060297121793, 1393796574908163946347162983661240005427201 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Written in binary, these numbers have exactly three 1 bits and the other bits are all 0's. This means that these numbers are of the sum of 1 plus two larger distinct powers of 2. - Alonso del Arte, Jul 08 2011 a(n) > A002110(n). [Reinhard Zumkeller, Jul 09 2011] Sequence is not monotone: a(12) > a(13). [Charles R Greathouse IV, Jul 11 2011] LINKS Charles R Greathouse IV, Table of n, a(n) for n = 1..14 MATHEMATICA list = {7}; For[max = 1; n = 2, n < 120, For[m = 0, m < n,   tal = 2*(2^n + 2^m) + 1; num = PrimeNu[tal];   If[num > max, AppendTo[list, tal]; max = num]   , m++], n++] (* Sarnbratt *) A084468 = Flatten[Table[2^m + 2^n + 1, {m, 2, 80}, {n, m - 1}]]; Flatten[Table[Take[Select[A084468, PrimeNu[#] == n &], 1], {n, 10}]] (* Alonso del Arte, Jul 08 2011 *) PROG (PARI) a(n)={   my(t);   for(a=2, 9e9,     t=1+1<

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Last modified June 19 03:38 EDT 2021. Contains 345125 sequences. (Running on oeis4.)