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A122581
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a(n) = a(n - 1) - 2*a(n - 2) + a(n - 3) + 2*(-2*a(n - 4) + a(n - 5)).
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3
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1, 1, 1, 1, 1, -2, -5, -2, 4, 13, 19, -5, -50, -65, -20, 118, 283, 187, -311, -914, -1001, 334, 3040, 4405, 835, -8273, -17030, -11189, 20068, 60178, 60427, -29165, -192491, -274310, -39845, 553798, 1070812, 635629, -1341437, -3836765, -3693914, 2237287, 12425356, 16921054, 1409755, -36343973
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,6
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COMMENTS
| This recursion is inspired by Ulam's early experiments in derivative recursions.
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FORMULA
| G.f.: -x*(1+2*x^2+x^3+5*x^4)/(-1+x-2*x^2+x^3-4*x^4+2*x^5). - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 18 2007
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MAPLE
| A122581 := proc(n) option remember ; if n <= 5 then 1; else A122581(n-1)-2*A122581(n-2)+A122581(n-3)+2*(-2*A122581(n-4)+A122581(n-5)) ; fi ; end: seq(A122581(n), n=1..80) ; - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Sep 18 2007
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MATHEMATICA
| a[0] = 1; a[1] = 1; a[2] = 1; a[3] = 1; a[4] = 1; a[n_] := a[n] = a[n - 1] - 2*a[n - 2] + a[n - 3] + 2*(-2*a[n - 4] + a[n - 5]); Table[a[n], {n, 0, 30}]
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CROSSREFS
| Sequence in context: A197805 A085072 A077200 * A151871 A010695 A021400
Adjacent sequences: A122578 A122579 A122580 * A122582 A122583 A122584
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KEYWORD
| sign
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AUTHOR
| Roger Bagula (rlbagulatftn(AT)yahoo.com), Sep 19 2006
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EXTENSIONS
| Edited by N. J. A. Sloane (njas(AT)research.att.com), Oct 01 2006
More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Sep 18 2007
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