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A245871 Number of length 2+2 0..n arrays with some pair in every consecutive three terms totalling exactly n. 1
10, 45, 100, 193, 318, 493, 712, 993, 1330, 1741, 2220, 2785, 3430, 4173, 5008, 5953, 7002, 8173, 9460, 10881, 12430, 14125, 15960, 17953, 20098, 22413, 24892, 27553, 30390, 33421, 36640, 40065, 43690, 47533, 51588, 55873, 60382, 65133, 70120, 75361 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

FORMULA

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

Conjectures from Colin Barker, Nov 04 2018: (Start)

G.f.: x*(10 + 15*x - 15*x^2 + 3*x^3 - x^4) / ((1 - x)^4*(1 + x)).

a(n) = 1 + 4*n + 7*n^2 + n^3 for n even.

a(n) = -2 + 4*n + 7*n^2 + n^3 for n odd.

(End)

EXAMPLE

Some solutions for n=10:

..9....1....8....0....9....0...10....4....3....5....8....4....3...10....3....9

..0....9....4....6....0...10....0....4....4....5....2....4....4....2....1....5

.10....1....6....4...10....0...10....6....6....9...10....6....6....8....9....1

.10....0....0....0....1....3....4....3....0....1....8....1....6....8....7....5

CROSSREFS

Row 2 of A245869.

Sequence in context: A238982 A292611 A275623 * A199350 A199516 A001488

Adjacent sequences:  A245868 A245869 A245870 * A245872 A245873 A245874

KEYWORD

nonn

AUTHOR

R. H. Hardin, Aug 04 2014

STATUS

approved

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Last modified June 16 21:55 EDT 2021. Contains 345080 sequences. (Running on oeis4.)