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 A202069 Number of arrays of n+2 integers in -1..1 with sum zero and the sum of every adjacent pair being odd 2
 2, 4, 2, 0, 6, 12, 6, 0, 20, 40, 20, 0, 70, 140, 70, 0, 252, 504, 252, 0, 924, 1848, 924, 0, 3432, 6864, 3432, 0, 12870, 25740, 12870, 0, 48620, 97240, 48620, 0, 184756, 369512, 184756, 0, 705432, 1410864, 705432, 0, 2704156, 5408312, 2704156, 0, 10400600 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Column 1 of A202076 LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = f(n mod 4) * binomial(2*z,z), where f(1)=1, f(2)=2, f(3)=1, f(0)=0, and z=floor((n+3)/4) EXAMPLE Some solutions for n=10 ..0....1...-1....1....0...-1....0....1....1....0....0....0....0...-1....0...-1 ..1....0....0....0....1....0...-1....0....0....1...-1....1...-1....0...-1....0 ..0...-1...-1...-1....0....1....0....1....1....0....0....0....0....1....0...-1 ..1....0....0....0...-1....0....1....0....0...-1...-1....1....1....0....1....0 ..0...-1....1...-1....0....1....0...-1....1....0....0....0....0....1....0...-1 ..1....0....0....0....1....0....1....0....0....1....1...-1...-1....0....1....0 ..0...-1....1....1....0...-1....0....1...-1....0....0....0....0...-1....0....1 .-1....0....0....0....1....0...-1....0....0...-1....1...-1....1....0...-1....0 ..0....1....1....1....0....1....0...-1...-1....0....0....0....0...-1....0....1 .-1....0....0....0...-1....0....1....0....0...-1....1....1...-1....0...-1....0 ..0....1...-1...-1....0...-1....0...-1...-1....0....0....0....0....1....0....1 .-1....0....0....0...-1....0...-1....0....0....1...-1...-1....1....0....1....0 CROSSREFS Sequence in context: A277659 A258711 A127278 * A300329 A094239 A273240 Adjacent sequences:  A202066 A202067 A202068 * A202070 A202071 A202072 KEYWORD nonn AUTHOR R. H. Hardin Dec 10 2011 STATUS approved

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Last modified January 22 17:33 EST 2019. Contains 319365 sequences. (Running on oeis4.)