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A002020
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a(n+1) = a(n) - n(n-1)a(n-1).
(Formerly M3876 N1588)
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4
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1, 1, 1, 1, -5, -17, 83, 593, -2893, -36101, 172195, 3421285, -15520165, -467129785, 1954015955, 86971636825, -323371713725, -21196564551725, 66760541581475, 6552909294409325, -16279195926455125, -2506384727801998625, 4330877561309153875
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,5
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REFERENCES
| R. Kelisky, The numbers generated by exp(arctan x), Duke Math. J., 26 (1959), 569-581.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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MAPLE
| f := proc(n) option remember; if n<=3 then 1 else f(n-1)-(n-1)*(n-2)*f(n-2); fi; end;
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CROSSREFS
| Sequence in context: A149753 A149754 A149755 * A038183 A149756 A036756
Adjacent sequences: A002017 A002018 A002019 * A002021 A002022 A002023
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KEYWORD
| sign,easy
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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