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A123151
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a(n)=f(n)*a(n - 3)/(n*(n - 1)*(n - 2)) where f(n)=(1/2)(2 + n + n^2)=A000124(n).
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0
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1, 1, 2, 7, 11, 32, 154, 319, 1184, 7084, 17864, 79328, 559636, 1643488, 8408768, 67715956, 225157856, 1294950272, 11647144432, 43005150496, 273234507392, 2702137508224, 10923308225984, 75685958547584, 813343389975424
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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MATHEMATICA
| f[n_Integer] = Module[{a}, a[n] /. RSolve[{a[n] == 2*a[n - 1] - a[n - 2] + 1, a[0] == 1, a[1] == 2}, a[n], n][[1]] // FullSimplify] Rationalize[N[Table[f[n], {n, 0, 25}], 100], 0]; a[n_] := a[n] = f[n]*a[n - 3]/(n*(n - 1)*(n - 2)); a[ 0] = 1; a[1] = 1; a[2] = 1; Table[a[n]*n!, {n, 0, 30}]
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CROSSREFS
| Cf. A000124.
Sequence in context: A073602 A057025 A055469 * A026133 A026162 A025189
Adjacent sequences: A123148 A123149 A123150 * A123152 A123153 A123154
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KEYWORD
| nonn
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AUTHOR
| Roger Bagula (rlbagulatftn(AT)yahoo.com), Oct 01 2006
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EXTENSIONS
| Edited by N. J. A. Sloane (njas(AT)research.att.com), Oct 04 2006
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