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A003591
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Numbers of form 2^i*7^j, with i, j >= 0.
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12
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1, 2, 4, 7, 8, 14, 16, 28, 32, 49, 56, 64, 98, 112, 128, 196, 224, 256, 343, 392, 448, 512, 686, 784, 896, 1024, 1372, 1568, 1792, 2048, 2401, 2744, 3136, 3584, 4096, 4802, 5488, 6272, 7168, 8192, 9604, 10976, 12544, 14336, 16384, 16807, 19208, 21952, 25088
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| A204455(7*a(n)) = 7, and only for these numbers. - From Wolfdieter Lang, Feb 04 2012
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LINKS
| Vincenzo Librandi, Table of n, a(n) for n = 1..100
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MATHEMATICA
| fQ[n_] := PowerMod[14, n, n]==0; Select[Range[30000], fQ] (* Vincenzo Librandi, Feb 04 2012 *)
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PROG
| (PARI) list(lim)=my(v=List(), N); for(n=0, log(lim)\log(7), N=7^n; while(N<=lim, listput(v, N); N<<=1)); vecsort(Vec(v)) \\ Charles R Greathouse IV, Jun 28 2011
(PARI) isA003591(n)=n>>=valuation(n, 2); ispower(n, , &n); n==1||n==7 \\ Charles R Greathouse IV, Jun 28 2011
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CROSSREFS
| Sequence in context: A102824 A201364 A177805 * A029746 A018708 A018461
Adjacent sequences: A003588 A003589 A003590 * A003592 A003593 A003594
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KEYWORD
| nonn,changed
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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