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A066488
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Composite numbers n which divide A001045(n-1).
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1
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341, 1105, 1387, 1729, 2047, 2465, 2701, 2821, 3277, 4033, 4369, 4681, 5461, 6601, 7957, 8321, 8911, 10261, 10585, 11305, 13741, 13747, 13981, 14491, 15709, 15841, 16705, 18721, 19951, 23377, 29341, 30121, 30889, 31417, 31609, 31621, 34945
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Also composite numbers, n, such that ((2^n - 2)/3 + 1) == 2^n -1 == 1 (mod n).
An equivalent definition of this sequence: pseudoprimes to base 2 that are not divisible by 3. [From Arkadiusz Wesolowski, Nov 15 2011]
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MATHEMATICA
| a[0] = 0; a[1] = 1; a[n_] := a[n] = a[n - 1] + 2a[n - 2]; Select[ Range[50000], IntegerQ[a[ # - 1]/ # ] && !PrimeQ[ # ] && # != 1 & ]
fQ[n_] := ! PrimeQ@ n && Mod[((2^n - 2)/3 + 1), n] == Mod[2^n - 1, n] == 1; Select[ Range@ 35000, fQ]
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CROSSREFS
| Cf. A066047.
Sequence in context: A179839 A172255 A087835 * A083876 A068216 A038473
Adjacent sequences: A066485 A066486 A066487 * A066489 A066490 A066491
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KEYWORD
| easy,nonn
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AUTHOR
| Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 03 2002
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