OFFSET
0,5
FORMULA
a(n) = n*a(n-3) + a(n-4) for n >= 4. - Jianing Song, Oct 10 2018
MATHEMATICA
M[n_] := {{0, 0, n, 1}, {1, 0, 0, 0}, {0, 1, 0, 0}, {0, 0, 1, 0}};
v[0] = {0, 0, 0, 1};
v[n_] := v[n] = M[n].v[n - 1];
a = Table[v[n][[1]], {n, 0, 30}]
PROG
(PARI) a(n) = if(n<4, n==1, n*a(n-3) + a(n-4)) \\ Jianing Song, Oct 10 2018
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Roger L. Bagula, Jun 19 2007
EXTENSIONS
Edited, new name, and offset corrected by Jianing Song, Oct 10 2018
STATUS
approved