A246894 Number of length 2+4 0..n arrays with some pair in every consecutive five terms totalling exactly n.

58, 673, 3364, 12481, 33294, 79345, 159688, 303169, 521890, 866881, 1351788, 2057473, 2996854, 4289041, 5943184, 8125825, 10838538, 14305249, 18515380, 23760961, 30013918, 37645873, 46605144, 57355201, 69813874, 84549505

Offset: 1

Author

R. H. Hardin, Sep 06 2014

Keywords

• nonn

Examples

			Some solutions for n=6:
..4....4....0....0....5....2....5....4....0....2....4....4....5....4....4....3
..2....4....3....0....5....3....3....5....6....3....6....0....5....2....4....6
..4....5....4....3....2....4....2....0....6....5....1....1....4....3....6....5
..2....0....3....6....5....2....3....0....3....5....2....0....1....2....5....1
..6....1....6....2....1....2....4....1....3....1....4....5....0....1....2....3
..0....1....4....4....5....4....3....3....3....1....5....6....1....4....0....4
		

Links

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

Crossrefs

Row 2 of A246892.

Formula

Empirical: a(n) = 2*a(n-1) + 3*a(n-2) - 8*a(n-3) - 2*a(n-4) + 12*a(n-5) - 2*a(n-6) - 8*a(n-7) + 3*a(n-8) + 2*a(n-9) - a(n-10).

Conjectures from Colin Barker, Nov 07 2018: (Start)

G.f.: x*(58 + 557*x + 1844*x^2 + 4198*x^3 + 3740*x^4 + 2876*x^5 - 268*x^6 - 1486*x^7 + 2*x^8 - x^9) / ((1 - x)^6*(1 + x)^4).

a(n) = 1 - 72*n + 146*n^2 - 57*n^3 + 31*n^4 + 6*n^5 for n even.

a(n) = -101 + 84*n + 99*n^2 - 61*n^3 + 31*n^4 + 6*n^5 for n odd.

(End)