A183947 Number of strings of numbers x(i=1..n) in 0..3 with sum i^2*x(i) equal to n^2*3

1, 1, 2, 4, 10, 26, 61, 147, 339, 771, 1721, 3770, 8123, 17233, 36041, 74322, 151368, 304614, 606305, 1194266, 2329462, 4501905, 8624652, 16386814, 30891283, 57801169, 107387377, 198165046, 363321016, 662012254, 1199130676, 2159720707

Offset

1,3

Comments

Column 3 of A183953

Links

R. H. Hardin, Table of n, a(n) for n = 1..75

Example

All solutions for n=4
..3....2....1....0
..1....3....1....0
..1....2....3....0
..2....1....1....3

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, 3];
Table[a[n], {n, 1, 40}] (* Jean-François Alcover, Jul 22 2022, after R. J. Mathar in A183953 *)

Crossrefs

Sequence in context: A007021 A100605 A247395 * A154322 A090031 A055775

Adjacent sequences: A183944 A183945 A183946 * A183948 A183949 A183950

Keyword

nonn

Author

R. H. Hardin, Jan 08 2011

Status

approved