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A050989
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7-idempotent numbers.
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5
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1, 56, 1764, 41160, 792330, 13311144, 201885684, 2826399576, 37096494435, 461645264080, 5493578642552, 62926446269232, 697434779483988, 7510836086750640, 78863778910881720, 809668130151718992
(list; graph; refs; listen; history; internal format)
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OFFSET
| 7,2
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LINKS
| Vincenzo Librandi, Table of n, a(n) for n = 7..400
Eric Weisstein's World of Mathematics, Idempotent Number
Index to sequences with linear recurrences with constant coefficients, signature (56,-1372,19208,-168070,941192,-3294172,6588344,-5764801).
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FORMULA
| a(n) = C(n, 7)*7^(n-7).
G.f.: x^7/(1-7*x)^8.
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MAPLE
| seq(binomial(n+7, 7)*7^n, n=0..17); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Aug 01 2008
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PROG
| (Sage) [lucas_number2(n, 7, 0)*binomial(n, 7)/7^7 for n in xrange(7, 23)] # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Mar 13 2009]
(PARI) a(n)=binomial(n, 7)*7^(n-7) \\ Charles R Greathouse IV, Sep 03 2011
(MAGMA) [7^(n-7)* Binomial(n, 7): n in [7..30]]; // Vincenzo Librandi, Oct 16 2011
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CROSSREFS
| Cf. A001788, A036216, A040075, A050982, A050988, A059297, A059300.
Sequence in context: A035723 A035799 A017719 * A140406 A075512 A000504
Adjacent sequences: A050986 A050987 A050988 * A050990 A050991 A050992
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KEYWORD
| nonn,easy
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AUTHOR
| Eric Weisstein (eric(AT)weisstein.com)
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