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a(n) = Sum_{k = 0..4} (n+k)! C(4,k).
(Formerly M5134 N2225)
4

%I M5134 N2225 #25 Feb 01 2022 01:32:20

%S 23,65,261,1370,8742,65304,557400,5343120,56775600,661933440,

%T 8397406080,115123680000,1695705580800,26701944192000,447579574041600,

%U 7955978033203200,149473718634240000,2959340324548608000,61578385989120000000,1343454891288846336000

%N a(n) = Sum_{k = 0..4} (n+k)! C(4,k).

%D N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

%H T. D. Noe, <a href="/A001346/b001346.txt">Table of n, a(n) for n = -1..100</a>

%H E. Biondi, L. Divieti, G. Guardabassi, <a href="http://dx.doi.org/10.4153/CJM-1970-003-9">Counting paths, circuits, chains and cycles in graphs: A unified approach</a>, Canad. J. Math. 22 1970 22-35.

%t Join[{23}, Table[Sum[(n + k)! Binomial[4, k], {k, 0, 4}], {n, 0, 20}]] (* _T. D. Noe_, Jun 28 2012 *)

%o (PARI) a(n) = if (n==-1, 23, sum(k=0, 4, (n+k)!*binomial(4, k))); \\ _Michel Marcus_, Jun 30 2017

%Y Cf. A001345, A001347.

%K nonn

%O -1,1

%A _N. J. A. Sloane_