A189321 Number of nondecreasing arrangements of n+2 numbers in 0..4 with the last equal to 4 and each after the second equal to the sum of one or two of the preceding four.

7, 12, 20, 32, 49, 70, 94, 120, 148, 178, 210, 244, 280, 318, 358, 400, 444, 490, 538, 588, 640, 694, 750, 808, 868, 930, 994, 1060, 1128, 1198, 1270, 1344, 1420, 1498, 1578, 1660, 1744, 1830, 1918, 2008, 2100, 2194, 2290, 2388, 2488, 2590, 2694, 2800, 2908

Offset

1,1

Comments

Column 4 of A189326.

Links

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

Formula

Empirical: a(n) = n^2 + 11*n - 32 for n>5.

Empirical g.f.: x*(7 - 9*x + 5*x^2 + x^3 + x^4 - x^5 - x^6 - x^7) / (1 - x)^3. - Colin Barker, May 02 2018

Example

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

Crossrefs

Cf. A189326.

Sequence in context: A093330 A071247 A025006 * A273072 A273147 A272845

Adjacent sequences: A189318 A189319 A189320 * A189322 A189323 A189324

Keyword

nonn

Author

R. H. Hardin, Apr 20 2011

Status

approved