A183948 Number of strings of numbers x(i=1..n) in 0..4 with sum i^2*x(i) equal to n^2*4.

1, 2, 3, 8, 27, 78, 219, 649, 1805, 4987, 13179, 34331, 87203, 217281, 532073, 1278041, 3025466, 7046194, 16192534, 36706373, 82197783, 181900279, 398099637, 862217855, 1848842707, 3927404946, 8267742253, 17257223344, 35726693834

Offset: 1

Author

R. H. Hardin, Jan 08 2011

Keywords

• nonn

Comments

Column 4 of A183953

Examples

			Some solutions for n=6
..0....4....2....3....4....0....3....2....2....0....4....0....2....3....4....2
..2....1....2....3....4....3....0....1....4....2....1....3....1....4....1....1
..2....2....1....2....3....0....1....0....2....1....1....1....1....0....4....4
..2....2....4....0....0....2....2....1....0....1....1....3....2....4....4....1
..2....2....1....3....1....4....4....2....0....3....3....3....1....1....0....2
..1....1....1....1....2....0....0....2....3....1....1....0....2....1....1....1
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..60

Programs

Mathematica

r[n_, k_, s_] := r[n, k, s] = Which[s < 0, 0, n == 0, If[s == 0, 1, 0], True, Sum[r[n - 1, k, s - c*n^2], {c, 0, k}]];
T[n_, k_] := r[n, k, k*n^2];
a[n_] := T[n, 4];
Table[a[n], {n, 1, 40}] (* Jean-François Alcover, Jul 22 2022, after R. J. Mathar in A183953 *)