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A193647 Number of arrays of -7..7 integers x(1..n) with every x(i) in a subsequence of length 1 or 2 with sum zero 2
1, 15, 43, 267, 1065, 5377, 23801, 113191, 517371, 2416835, 11155313, 51830017, 239940625, 1112996767, 5157111051, 23910123931, 110818577241, 513715752705, 2381164556233, 11037736722167, 51163163871835, 237160332965907 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 7 of A193648

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..200

FORMULA

Empirical: a(n) = 2*a(n-1) +12*a(n-2) +a(n-3).

Empirical: G.f.: -x*(1+13*x+x^2) / ( -1+2*x+12*x^2+x^3 ). - R. J. Mathar, Feb 19 2015

EXAMPLE

Some solutions for n=6

.-1...-3....3....5....7....5....6....0....1....0...-5...-3...-7....1...-4....0

..1....3...-3...-5...-7...-5...-6....0...-1....7....5....3....7...-1....4....2

.-4....4....0...-3....0....2....6....7....0...-7...-5...-6...-7....4...-6...-2

..4...-4....0....3...-2...-2...-6...-7....0....0....6....6....7...-4....6....6

.-4....3...-1...-7....2....0....7...-3....6....3...-6...-7...-4...-2....3...-6

..4...-3....1....7...-2....0...-7....3...-6...-3....6....7....4....2...-3....0

CROSSREFS

Sequence in context: A124708 A204734 A126369 * A133343 A027845 A201810

Adjacent sequences:  A193644 A193645 A193646 * A193648 A193649 A193650

KEYWORD

nonn

AUTHOR

R. H. Hardin Aug 02 2011

STATUS

approved

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Last modified November 20 10:09 EST 2019. Contains 329334 sequences. (Running on oeis4.)