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A107386
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a(n) = 2*a(n-1)-2*a(n-3)+a(n-4), n>6.
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1
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0, 1, 1, 2, 2, 7, 9, 16, 20, 29, 35, 46, 54, 67, 77, 92, 104, 121, 135, 154, 170, 191, 209, 232, 252, 277, 299, 326, 350, 379, 405, 436, 464, 497, 527, 562, 594, 631, 665, 704, 740, 781, 819, 862, 902, 947, 989, 1036, 1080, 1129
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,4
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FORMULA
| G.f.: x*(-4*x^4+2*x^5+x-1)/((1+x)*(x-1)^3). [ Sep 28 2009]
a(n)= n^2/2-3*n/2+1-(-1)^n, n>2. [ Sep 28 2009]
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MATHEMATICA
| Clear[M, m, v, aa] (*A107386*)m = 2; M = {{0, 1, 0, 0}, {0, 0, 1, 0}, {0, 0, 0, 1}, {1, m, 0, - m}}; Expand[Det[M - x*IdentityMatrix[4]]] ; NSolve[Det[M - x*IdentityMatrix[4]] == 0, x] ; v[1] = {0, 1, 1, 2}; v[n_] := v[n] = M . v[n - 1]; digits = 50; aa = Table[Abs[v[n][[1]]], {n, 1, digits}]
a=2; lst={0, 1, 1, a}; Do[a=n^2-a; AppendTo[lst, a], {n, 2, 5!}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Dec 17 2008]
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CROSSREFS
| Cf. A107387, A107388, A107389.
Sequence in context: A011022 A070910 A189040 * A095021 A101372 A133374
Adjacent sequences: A107383 A107384 A107385 * A107387 A107388 A107389
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KEYWORD
| nonn,easy
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AUTHOR
| Roger L. Bagula (rlbagulatftn(AT)yahoo.com), May 24 2005, corrected Sep 04 2008
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EXTENSIONS
| Definition replaced by recurrence by the Associate Editors of the OEIS, Sep 28 2009
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