A250355 Number of length 6 arrays x(i), i=1..6 with x(i) in i..i+n and no value appearing more than 2 times.

64, 622, 3349, 12734, 38543, 99344, 226247, 467642, 894599, 1606988, 2740319, 4473302, 7036127, 10719464, 15884183, 22971794, 32515607, 45152612, 61636079, 82848878, 109817519, 143726912, 185935847, 237993194, 301654823, 378901244

Offset

1,1

Links

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

Formula

Empirical: a(n) = n^6 + 6*n^5 - 5*n^4 + 55*n^3 + 25*n^2 - 61*n + 98 for n>3.

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

G.f.: x*(64 + 174*x + 339*x^2 + 113*x^3 + 204*x^4 + 168*x^5 - 847*x^6 + 783*x^7 - 336*x^8 + 58*x^9) / (1 - x)^7.

a(n) = 7*a(n-1) - 21*a(n-2) + 35*a(n-3) - 35*a(n-4) + 21*a(n-5) - 7*a(n-6) + a(n-7) for n>10.

(End)

Example

Some solutions for n=6:
..1....4....6....5....1....2....1....6....0....3....0....6....2....1....3....5
..1....3....6....2....7....2....5....6....5....5....4....5....3....1....3....1
..7....8....2....4....5....4....3....5....7....6....8....8....7....8....8....4
..3....8....5....7....5....7....8....7....4....8....9....3....8....5....5....3
..4....9....4....8....9...10....4...10....6....7...10....9....8....6....5....4
..9...11....7....5...10....9....8....9....6....7....8...10...10....9....9....6

Crossrefs

Row 6 of A250351.

Sequence in context: A229401 A232052 A200788 * A045789 A000525 A067476

Adjacent sequences: A250352 A250353 A250354 * A250356 A250357 A250358

Keyword

nonn

Author

R. H. Hardin, Nov 19 2014

Status

approved