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Search: id:A004208
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| A004208 |
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a(n) = n(2n-1)!!- Sum a(k)(2n-2k-1)!!.
(Formerly M3985)
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+0
4
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| 1, 5, 37, 353, 4081, 55205, 854197, 14876033, 288018721, 6138913925, 142882295557, 3606682364513, 98158402127761, 2865624738913445, 89338394736560917, 2962542872271918593, 104128401379446177601
(list; graph; listen)
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OFFSET
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1,2
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FORMULA
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x+5/2*x^2+37/3*x^3+353/4*x^4+4081/5*x^5+55205/6*x^6+... = log(1+x+3*x^2+15*x^3+105*x^4+945*x^5+10395*x^6+...) where [1, 1, 3, 15, 105, 945, 10395, ...] = A001147(double factorials) . - Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Jun 20 2006
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MAPLE
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df := proc(n) product(2*k-1, k=1..n) end: a[1] := 1: for n from 2 to 30 do a[n] := n*df(n)-sum(a[k]*df(n-k), k=1..n-1) od;
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CROSSREFS
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Equals 2 * A000698(n+1), n>0.
Adjacent sequences: A004205 A004206 A004207 this_sequence A004209 A004210 A004211
Sequence in context: A078253 A006442 A084212 this_sequence A112698 A025168 A084358
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KEYWORD
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nonn
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AUTHOR
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njas
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EXTENSIONS
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Description corrected by Jeremy Magland (magland(AT)math.byu.edu), Jan 07 2000
More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Dec 21 2003
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