A246739 Number of length 2+4 0..n arrays with no pair in any consecutive five terms totalling exactly n.

2, 16, 260, 1096, 5430, 15960, 47432, 109552, 246890, 483520, 920652, 1606776, 2735390, 4392136, 6907280, 10419040, 15447762, 22202352, 31455380, 43507240, 59453702, 79710136, 105775320, 138205776, 178991930, 228860320, 290390492

Offset

1,1

Links

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

Formula

Empirical: a(n) = 3*a(n-1) + a(n-2) - 11*a(n-3) + 6*a(n-4) + 14*a(n-5) - 14*a(n-6) - 6*a(n-7) + 11*a(n-8) - a(n-9) - 3*a(n-10) + a(n-11).

Conjectures from Colin Barker, Nov 06 2018: (Start)

G.f.: 2*x*(1 + 5*x + 105*x^2 + 161*x^3 + 1023*x^4 + 655*x^5 + 2211*x^6 + 523*x^7 + 1076*x^8) / ((1 - x)^7*(1 + x)^4).

a(n) = -58*n + 111*n^2 - 87*n^3 + 36*n^4 - 8*n^5 + n^6 for n even.

a(n) = -70 + 80*n + 34*n^2 - 71*n^3 + 36*n^4 - 8*n^5 + n^6 for n odd.

(End)

Example

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

Crossrefs

Row 2 of A246737.

Sequence in context: A114039 A090305 A358145 * A304317 A351918 A326272

Adjacent sequences: A246736 A246737 A246738 * A246740 A246741 A246742

Keyword

nonn

Author

R. H. Hardin, Sep 02 2014

Status

approved