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A015503
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a(1) = 1, a(n) = Sum_{k=1..n-1} ((4^k - 1)/3)*a(k).
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10
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1, 1, 6, 132, 11352, 3882384, 5303336544, 28966824203328, 632809241545903488, 55296137144764138588416, 19327437631660830304254690816, 27021729207700270170039091739231232, 151116480551518237100547636877027177224192
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OFFSET
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1,3
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LINKS
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FORMULA
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MATHEMATICA
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a[n_, m_]:= a[n, m]= If[n<3, 1, (m^(n-1)+m-2)*a[n-1, m]/(m-1)];
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PROG
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(Magma) [n le 2 select 1 else ((4^(n-1)+2)/3)*Self(n-1): n in [1..15]]; // Vincenzo Librandi, Nov 11 2012
(SageMath)
def a(n, m): return 1 if (n<3) else (m^(n-1) + m-2)*a(n-1, m)/(m-1)
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CROSSREFS
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Sequences with the recurrence a(n) = (m^(n-1) + m-2)*a(n-1)/(m-1): A036442 (m=2), A015502 (m=3), this sequence (m=4), A015506 (m=5), A015507 (m=6), A015508 (m=7), A015509 (m=8), A015511 (m=9), A015512 (m=10), A015513 (m=11), A015515 (m=12).
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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