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A221962 Number of -3..3 arrays of length n with the sum ahead of each element differing from the sum following that element by 3 or less. 1
7, 49, 175, 833, 3647, 16513, 73983, 332801, 1495039, 6719489, 30195711, 135700481, 609828863, 2740551681, 12315918335, 55347249153, 248728256511, 1117774675969, 5023233736703, 22574207598593, 101447567933439, 455901232234497 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 3 of A221967.

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..144

FORMULA

Empirical: a(n) = 3*a(n-1) + 8*a(n-2) - 4*a(n-3) - 8*a(n-4).

Empirical g.f.: 7*x*(1 + 4*x - 4*x^2 - 8*x^3) / ((1 + x)*(1 - 4*x - 4*x^2 + 8*x^3)). - Colin Barker, Aug 11 2018

EXAMPLE

Some solutions for n=6:

..1...-3....1....0...-2....2...-3...-2....1....1....1....0...-3...-2....2....2

.-2...-1....1....1....0...-2....2....1....0...-3...-2....0....0....2...-2....0

..2....2...-3...-2....3...-1....1....0....0....1....3....0....1....2....0....0

.-2...-2....0....3...-2....1...-1....3...-1....0....0....0...-1...-2....1...-3

.-2....1....0...-2....2....2....1...-3....3...-1....1....2....0....2...-2....2

..1...-1....1...-1...-2...-1...-2...-1...-3....1....0...-1...-1...-2....3....0

CROSSREFS

Cf. A221967.

Sequence in context: A262269 A163827 A206989 * A294292 A015953 A206931

Adjacent sequences:  A221959 A221960 A221961 * A221963 A221964 A221965

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 01 2013

STATUS

approved

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Last modified September 23 20:42 EDT 2021. Contains 347617 sequences. (Running on oeis4.)