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A114633
a(n) = (n+1)*(n+2)/2 * Sum_{k=0..floor(n/2)} n!/(n-2*k)!.
1
1, 3, 18, 70, 555, 2961, 31108, 213228, 2799765, 23455135, 369569046, 3659001138, 67261566463, 768390239085, 16142775951240, 209002145031256, 4939689441079593, 71478733600689723, 1877081987610245530, 30021068112289683870, 867211878275933435091, 15190660464818580038473
OFFSET
0,2
COMMENTS
Formula was found by Paul D. Hanna.
Related to logarithmic numbers A002104.
LINKS
FORMULA
a(n) = A087208(n)*(n+1)*(n+2)/2. - Paul D. Hanna
E.g.f.: exp(x)/(1-x^2)*(x^2/2) (with offset 2). - Zerinvary Lajos, Apr 03 2009
MAPLE
a:= n-> (n+1)*(n+2)/2*sum(n!/(n-2*k)!, k=0..floor(n/2)): seq(a(n), n=0..20);
MATHEMATICA
Rest[Rest[With[{nn=25}, CoefficientList[Series[Exp[x]/(1 - x^2)(x^2/2), {x, 0, nn}], x] Range[0, nn]!]]] (* Vincenzo Librandi, Sep 03 2017 *)
CROSSREFS
Sequence in context: A374487 A098522 A174764 * A135070 A073961 A305623
KEYWORD
nonn
AUTHOR
Creighton Dement, Feb 17 2006
EXTENSIONS
More terms from Vincenzo Librandi, Sep 03 2017
STATUS
approved