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A024392
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a(n) = 3rd elementary symmetric function of the first n+2 positive integers congruent to 2 mod 3.
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6
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80, 806, 4040, 14155, 39655, 95200, 204036, 400830, 734910, 1273910, 2107820, 3353441, 5159245, 7710640, 11235640, 16010940, 22368396, 30701910, 41474720, 55227095, 72584435, 94265776, 121092700, 153998650, 194038650, 242399430
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OFFSET
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1,1
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LINKS
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Vincenzo Librandi, Table of n, a(n) for n = 1..5000
Index entries for linear recurrences with constant coefficients, signature (7,-21,35,-35,21,-7,1).
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FORMULA
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a(n) = n*(n+1)*(n+2)*(3*n+7)*(9*n^2+33*n+22)/48.
G.f.: -x*(80+246*x+78*x^2+x^3) / (x-1)^7 . - R. J. Mathar, Oct 08 2011
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MATHEMATICA
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Table[n (n + 1) (n + 2) (3 n + 7) (9 n^2 + 33 n + 22) / 48, {n, 1, 50}] (* Vincenzo Librandi, Jul 07 2019 *)
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PROG
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(MAGMA) [n*(n+1)*(n+2)*(3*n+7)*(9*n^2+33*n+22)/48: n in [1..40]]; // Vincenzo Librandi, Jul 07 2019
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CROSSREFS
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Sequence in context: A164753 A279745 A062911 * A200550 A052519 A246545
Adjacent sequences: A024389 A024390 A024391 * A024393 A024394 A024395
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KEYWORD
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nonn,easy
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AUTHOR
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Clark Kimberling
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STATUS
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approved
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