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Search: id:A112503
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| 1, 20, 225, 1882, 13070, 79872, 444902, 2311828, 11388999, 53820068, 246112783, 1096379070, 4782801180, 20515294320, 86808499020, 363304109640, 1507010836605, 6206407299540, 25412183425165, 103563957886370
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OFFSET
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0,2
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COMMENT
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For a combinatorial formula see A112500, case k=4.
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FORMULA
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G.f.: 1/product((1-j*x)^(5-j), j=1..4) = 1/(((1-x)^4)*((1-2*x)^3)*((1-3*x)^2)*(1-4*x)).
a(n) = 7813/324 + (2251/432)*(n+1) + (31/36)*binomial(n+2, 2) +(1/12)*binomial(n+3, 3) +(-1344 -256*(n+1) - 64*binomial(n+2, 2))*2^n + (6561/4 - (6561/16)*(n+1))*3^n + (32768/81)*4^n, n>=0 (from partial fractions for g.f.).
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CROSSREFS
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Adjacent sequences: A112500 A112501 A112502 this_sequence A112504 A112505 A112506
Sequence in context: A140354 A000833 A054329 this_sequence A007160 A023018 A073386
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KEYWORD
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nonn,easy
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AUTHOR
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Wolfdieter Lang (wolfdieter.lang_AT_physik_DOT_uni-karlsruhe_DOT_de), Oct 14 2005
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