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 A221235 Number of nonnegative integer arrays of length n summing to n without adjacent equal values. 3
 1, 1, 2, 7, 14, 30, 76, 188, 444, 1075, 2656, 6504, 15926, 39316, 97252, 240597, 596686, 1482971, 3689768, 9191590, 22927718, 57253334, 143101896, 358003469, 896391914, 2246149936, 5632310800, 14132640565, 35483595966, 89141668532, 224061612932, 563473301874 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Alois P. Heinz, Table of n, a(n) for n = 0..500 (first 210 terms from R. H. Hardin) FORMULA a(n) = A106351(2n,n). - Alois P. Heinz, Oct 12 2017 EXAMPLE All solutions for n=3 ..1....2....0....2....0....0....1 ..2....1....3....0....2....1....0 ..0....0....0....1....1....2....2 MAPLE b:= proc(n, h, t) option remember; `if`(t<2, `if`(n<>h, 1, 0), add(`if`(h=j, 0, b(n-j, `if`(j>n-j, -1, j), t-1)), j=0..n)) end: a:= n-> b(n, -1, n): seq(a(n), n=0..35); # Alois P. Heinz, Oct 15 2017 MATHEMATICA b[n_, h_, t_] := b[n, h, t] = If[t < 2, If[n != h, 1, 0], Sum[If[h == j, 0, b[n-j, If[j > n-j, -1, j], t-1]], {j, 0, n}]]; a[n_] := b[n, -1, n]; Table[a[n], {n, 0, 35}] (* Jean-François Alcover, Apr 28 2022, after Alois P. Heinz *) CROSSREFS Cf. A106351. Sequence in context: A221318 A221319 A221320 * A224916 A258321 A034791 Adjacent sequences: A221232 A221233 A221234 * A221236 A221237 A221238 KEYWORD nonn AUTHOR R. H. Hardin, Jan 10 2013 EXTENSIONS a(0)=1 prepended by Alois P. Heinz, Oct 15 2017 STATUS approved

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Last modified September 22 21:28 EDT 2023. Contains 365531 sequences. (Running on oeis4.)