A189324 Number of nondecreasing arrangements of n+2 numbers in 0..7 with the last equal to 7 and each after the second equal to the sum of one or two of the preceding four.

11, 17, 31, 51, 91, 157, 253, 374, 509, 649, 789, 929, 1069, 1209, 1349, 1489, 1629, 1769, 1909, 2049, 2189, 2329, 2469, 2609, 2749, 2889, 3029, 3169, 3309, 3449, 3589, 3729, 3869, 4009, 4149, 4289, 4429, 4569, 4709, 4849, 4989, 5129, 5269, 5409, 5549

Offset

1,1

Comments

Column 7 of A189326.

Links

R. H. Hardin, Table of n, a(n) for n = 1..200

Formula

Empirical: a(n) = 140*n - 751 for n>8.

Empirical g.f.: x*(11 - 5*x + 8*x^2 + 6*x^3 + 20*x^4 + 26*x^5 + 30*x^6 + 25*x^7 + 14*x^8 + 5*x^9) / (1 - x)^2. - Colin Barker, May 02 2018

Example

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

Crossrefs

Cf. A189326.

Sequence in context: A208573 A142718 A258866 * A127703 A165667 A339180

Adjacent sequences: A189321 A189322 A189323 * A189325 A189326 A189327

Keyword

nonn

Author

R. H. Hardin, Apr 20 2011

Status

approved