OFFSET
4,2
COMMENTS
From the game of Mousetrap.
LINKS
G. C. Greubel, Table of n, a(n) for n = 4..450
D. J. Mundfrom, A problem of permutations: the Game of "Mousetrap", Eur. J. Combinat. 15 (1994) 555-560.
FORMULA
a(n) = (n-2)! - 3*(n-3)! + 2*(n-4)! if n > 5. - R. J. Mathar, Oct 02 2008
E.g.f.: (x*(1020 - 1290*x + 340*x^2 - 15*x^3 + 3*x^4) + 60*(17 - 30*x + 15*x^2 - 2*x^3)*log(1-x))/360. - G. C. Greubel, Feb 21 2019
MAPLE
0, 3, seq((n^2-8*n+17)*factorial(n-4), n=6..30); # Muniru A Asiru, Feb 22 2019
MATHEMATICA
Join[{0, 3}, Table[(n^2-8*n+17)*(n-4)!, {n, 6, 30}]] (* G. C. Greubel, Feb 21 2019 *)
PROG
(PARI) for(n=4, 30, print1(if(n==4, 0, if(n==5, 3, (n^2-8*n+17)*(n-4)!)), ", ")) \\ G. C. Greubel, Feb 21 2019
(Magma) [0, 3] cat [(n^2-8*n+17)*Factorial(n-4): n in [6..30]]; // G. C. Greubel, Feb 21 2019
(Sage) [0, 3] + [(n^2-8*n+17)*factorial(n-4) for n in (6..30)] # G. C. Greubel, Feb 21 2019
(GAP) Concatenation([0, 3], List([6..30], n-> (n^2-8*n+17)*Factorial(n-4) )) # G. C. Greubel, Feb 21 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
Offset changed to 4, more terms, better definition and link from R. J. Mathar, Oct 02 2008
STATUS
approved