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A250321 Number of length 2+2 0..n arrays with the sum of second differences squared multiplied by some arrangement of +-1 equal to zero. 2
8, 25, 60, 117, 200, 321, 480, 681, 940, 1253, 1624, 2073, 2592, 3185, 3876, 4653, 5520, 6505, 7592, 8785, 10116, 11565, 13136, 14865, 16728, 18729, 20908, 23237, 25720, 28401, 31248, 34265, 37500, 40917, 44520, 48361, 52400, 56641, 61140, 65853, 70784 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Row 2 of A250320.
LINKS
FORMULA
Empirical: a(n) = 2*a(n-1) - a(n-2) + 2*a(n-3) - 4*a(n-4) + 2*a(n-5) - a(n-6) + 2*a(n-7) - a(n-8).
Empirical g.f.: x*(8 + 9*x + 18*x^2 + 6*x^3 + 8*x^4 + 2*x^5 + 2*x^6 - x^7) / ((1 - x)^4*(1 + x + x^2)^2). - Colin Barker, Mar 19 2018
EXAMPLE
Some solutions for n=6:
..2....5....6....1....4....1....6....3....3....2....6....0....3....1....0....0
..2....6....1....0....1....3....5....4....4....1....1....0....0....4....3....4
..0....0....6....1....6....3....3....3....0....2....1....2....6....3....1....1
..0....1....1....4....3....5....0....0....1....5....6....6....3....6....4....5
CROSSREFS
Cf. A250320.
Sequence in context: A270867 A360201 A004640 * A011924 A370081 A346522
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 18 2014
STATUS
approved

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Last modified May 23 21:14 EDT 2024. Contains 372765 sequences. (Running on oeis4.)