A123280 Number of permutations of n distinct letters (ABCD...) each of which appears 4 times and having two fixed points.

0, 16, 4536, 8607744, 42506546320, 456702275019600, 9418598754396188616, 340409678708013417037696, 20126978659582117984569511584, 1844705433432528416880778883815440

Offset

0,2

Links

Table of n, a(n) for n=0..9.

Example

1
0, 0, "0", 0, 1
1, 0, "16", 0, 36, 0, 16, 0, 1
346, 1824, "4536", 7136, 7947, 6336, 3936, 1728, 684, 128, 48, 0, 1
748521, 3662976, "8607744", 12880512, 13731616, 11042688, 6928704, 3458432, 1395126, 453888, 122016, 25344, 4824, 512, 96, 0, 1
etc...

Maple

p := (x, k)->k!^2*sum(x^j/((k-j)!^2*j!), j=0..k); R := (x, n, k)->p(x, k)^n; f := (t, n, k)->sum(coeff(R(x, n, k), x, j)*(t-1)^j*(n*k-j)!, j=0..n*k); for n from 0 to 5 do seq(coeff(f(t, n, 4), t, m)/4!^n, m=0..4*n); od;

Crossrefs

Cf. A059060.

Sequence in context: A176369 A090045 A201241 * A289904 A181028 A258583

Adjacent sequences: A123277 A123278 A123279 * A123281 A123282 A123283

Keyword

nonn

Author

Zerinvary Lajos, Nov 07 2006

Status

approved