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A144656
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Defined by a(n) = (n mod 2) if n<=3, otherwise a(n) = (n^2-5n+7)*(n-2)*a(n-2)/(n-3) + (n^2-5n+7)*a(n-2) - (n-2)*a(n-3)/(n-3).
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1
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0, 1, 0, 1, 4, 49, 900, 24649, 944784, 48455521, 3210355600, 267186643801, 27307626948900, 3363915436531441, 491705171699154084, 84158959760104032049, 16675767262618669710400, 3787671541267275818341249, 977702867682508392324162624, 284628954669920840314598014801
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,5
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COMMENTS
| Terms are squares; square roots give A001053.
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REFERENCES
| S. B. Ekhad, Problem 10356, Amer. Math. Monthly, 101 (1994), 75.
M. E. Larsen, Summa Summarum, A. K. Peters, Wellesley, MA, 2007; see p. 35.
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MAPLE
| a:=proc(n) option remember; local m;
if n=0 then RETURN(0); fi;
if n=1 then RETURN(1); fi;
if n=2 then RETURN(0); fi;
if n=3 then RETURN(1); fi;
m:=n-3;
RETURN((m^2+m+1)*(m+1)*a(n-1)/m+(m^2+m+1)*a(n-2)-(m+1)*a(n-3)/m);
end;
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CROSSREFS
| Sequence in context: A055793 A202829 A204233 * A121275 A188682 A191301
Adjacent sequences: A144653 A144654 A144655 * A144657 A144658 A144659
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Jan 30 2009
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