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A247728 Number of length 2+3 0..n arrays with no disjoint pairs in any consecutive four terms having the same sum 1
8, 90, 456, 1592, 4344, 10098, 20816, 39264, 69000, 114650, 181848, 277560, 409976, 588882, 825504, 1132928, 1525896, 2021274, 2637800, 3396600, 4320888, 5436530, 6771696, 8357472, 10227464, 12418458, 14969976, 17924984, 21329400, 25232850 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Row 2 of A247726

LINKS

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

FORMULA

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

Empirical for n mod 2 = 0: a(n) = 1*n^5 + 1*n^4 + (9/2)*n^3 + (3/2)*n^2

Empirical for n mod 2 = 1: a(n) = 1*n^5 + 1*n^4 + (9/2)*n^3 + (3/2)*n^2 - (3/2)*n + (3/2).

Empirical G.f.: 2*x*(4+29*x+64*x^2+80*x^3+40*x^4+23*x^5) / ( (1+x)^2*(x-1)^6 ). - R. J. Mathar, Sep 23 2014

EXAMPLE

Some solutions for n=6

..6....5....2....0....1....3....1....1....6....3....6....3....0....6....6....4

..3....3....3....4....3....4....2....0....6....6....5....3....5....4....4....2

..2....3....0....0....1....1....2....6....6....1....0....2....1....0....0....6

..4....6....3....0....0....1....5....4....5....1....2....6....3....0....0....3

..2....5....3....1....0....3....2....0....2....2....0....6....4....1....5....4

CROSSREFS

Sequence in context: A045732 A077192 A128304 * A056784 A166769 A323960

Adjacent sequences:  A247725 A247726 A247727 * A247729 A247730 A247731

KEYWORD

nonn

AUTHOR

R. H. Hardin, Sep 23 2014

STATUS

approved

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Last modified May 25 02:26 EDT 2022. Contains 354047 sequences. (Running on oeis4.)