OFFSET
0,1
REFERENCES
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).
LINKS
T. D. Noe, Table of n, a(n) for n = 0..100
E. Biondi, L. Divieti, G. Guardabassi, Counting paths, circuits, chains and cycles in graphs: A unified approach, Canad. J. Math. 22 1970 22-35.
Philip Feinsilver and John McSorley, Zeons, Permanents, the Johnson Scheme, and Generalized Derangements, International Journal of Combinatorics, Volume 2011, Article ID 539030, 29 pages.
FORMULA
a(n) = ceiling( n!*(n^3 + 3*n^2 + 5*n + 2)*exp(1) ). - Mark van Hoeij, Nov 11 2009
G.f.: Q(0)*(1-x)^2/x^3 - 2/x + 1/x^2 - 1/x^3, where Q(k)= 1 + (2*k + 1)*x/( 1 - x - 2*x*(1-x)*(k+1)/(2*x*(k+1) + (1-x)/Q(k+1))); (continued fraction). - Sergei N. Gladkovskii, May 09 2013
MATHEMATICA
nn = 20; Range[0, nn]! CoefficientList[Series[6*Exp[x]/(1 - x)^4, {x, 0, nn}], x] (* T. D. Noe, Jun 28 2012 *)
PROG
(PARI) x='x+O('x^66); Vec(serlaplace(6*exp(x)/(1-x)^4)) \\ Joerg Arndt, May 09 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
Error in definition corrected Jan 30 2008
More terms from N. J. A. Sloane, Jan 30 2008
STATUS
approved