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

Author

R. H. Hardin, Sep 02 2014

Keywords

• nonn

Examples

			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
		

Links

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

Crossrefs

Row 2 of A246737.

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)