A245997 Number of length 2+2 0..n arrays with no pair in any consecutive three terms totalling exactly n

2, 12, 68, 208, 534, 1116, 2120, 3648, 5930, 9100, 13452, 19152, 26558, 35868, 47504, 61696, 78930, 99468, 123860, 152400, 185702, 224092, 268248, 318528, 375674, 440076, 512540, 593488, 683790, 783900, 894752, 1016832, 1151138, 1298188

Offset

1,1

Comments

Row 2 of A245995

Links

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

Formula

Empirical: a(n) = 3*a(n-1) -a(n-2) -5*a(n-3) +5*a(n-4) +a(n-5) -3*a(n-6) +a(n-7).

Empirical: G.f.: -2*x*(1+3*x+17*x^2+13*x^3+14*x^4) / ( (1+x)^2*(x-1)^5 ). - R. J. Mathar, Aug 10 2014

Example

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

Crossrefs

Sequence in context: A000954 A056636 A174327 * A377112 A128103 A359489

Adjacent sequences: A245994 A245995 A245996 * A245998 A245999 A246000

Keyword

nonn

Author

R. H. Hardin, Aug 09 2014

Status

approved