A250362 Number of length 4 arrays x(i), i=1..4 with x(i) in i..i+n and no value appearing more than 3 times.

16, 81, 255, 623, 1293, 2397, 4091, 6555, 9993, 14633, 20727, 28551, 38405, 50613, 65523, 83507, 104961, 130305, 159983, 194463, 234237, 279821, 331755, 390603, 456953, 531417, 614631, 707255, 809973, 923493, 1048547, 1185891, 1336305

Offset: 1

Author

R. H. Hardin, Nov 19 2014

Keywords

• nonn

Examples

			Some solutions for n=6:
..1....2....1....3....1....5....3....5....0....0....5....0....5....3....2....4
..2....3....5....7....4....6....4....3....3....2....6....5....4....4....4....6
..8....4....2....5....2....8....7....2....6....5....4....7....6....7....3....2
..3....6....6....9....9....6....7....4....8....7....5....6....7....9....4....9
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..210

Crossrefs

Row 4 of A250361.

Formula

Empirical: a(n) = n^4 + 4*n^3 + 6*n^2 + 3*n + 3 for n>1.

Conjectures from Colin Barker, Nov 13 2018: (Start)

G.f.: x*(16 + x + 10*x^2 - 2*x^3 - 2*x^4 + x^5) / (1 - x)^5.

a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5) for n>6.

(End)