A243464 Number of ways 2 domicules can be placed on an n X n square.
0, 0, 3, 110, 657, 2172, 5375, 11178, 20685, 35192, 56187, 85350, 124553, 175860, 241527, 324002, 425925, 550128, 699635, 877662, 1087617, 1333100, 1617903, 1946010, 2321597, 2749032, 3232875, 3777878, 4388985, 5071332, 5830247, 6671250, 7600053, 8622560
Offset: 0
Examples
a(2) = 3: +---+ +---+ +---+ |o-o| |o o| |o o| | | || || | X | |o-o| |o o| |o o| +---+ +---+ +---+.
Links
- Alois P. Heinz, Table of n, a(n) for n = 0..1000
Crossrefs
Column k=2 of A243424.
Programs
-
Maple
a:= n-> `if`(n=0, 0, (((8*n-24)*n-4)*n+63)*n-43): seq(a(n), n=0..50);
Formula
G.f.: x^2*(43*x^3-137*x^2-95*x-3)/(x-1)^5.
a(n) = -43+63*n-4*n^2-24*n^3+8*n^4 for n>0, a(0) = 0.