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 A223719 Number of n X 2 0..2 arrays with rows, antidiagonals and columns unimodal. 5
 9, 81, 484, 2116, 7396, 21904, 57121, 134689, 292681, 594441, 1140624, 2085136, 3655744, 6180196, 10118761, 16104169, 24990001, 37908649, 56340036, 82192356, 117896164, 166513216, 231861529, 318658201, 432681601, 580954609, 771950656 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Column 2 of A223725. LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = (1/576)*n^8 + (1/48)*n^7 + (41/288)*n^6 + (13/24)*n^5 + (793/576)*n^4 + (31/16)*n^3 + (119/48)*n^2 + (3/2)*n + 1. Conjectures from Colin Barker, Feb 19 2018: (Start) G.f.: x*(9 + 79*x^2 - 80*x^3 + 106*x^4 - 68*x^5 + 31*x^6 - 8*x^7 + x^8) / (1 - x)^9. a(n) = 9*a(n-1) - 36*a(n-2) + 84*a(n-3) - 126*a(n-4) + 126*a(n-5) - 84*a(n-6) + 36*a(n-7) - 9*a(n-8) + a(n-9) for n>9. (End) EXAMPLE Some solutions for n=3: ..1..0....2..0....1..2....2..0....1..1....2..0....0..2....2..1....1..1....2..2 ..1..2....1..2....1..2....0..0....2..2....2..1....2..0....1..1....2..1....1..2 ..2..1....1..0....1..2....0..1....0..1....0..0....2..0....1..2....1..1....1..1 CROSSREFS Sequence in context: A207719 A167717 A208079 * A270295 A214618 A343462 Adjacent sequences: A223716 A223717 A223718 * A223720 A223721 A223722 KEYWORD nonn AUTHOR R. H. Hardin, Mar 26 2013 STATUS approved

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Last modified February 29 20:48 EST 2024. Contains 370428 sequences. (Running on oeis4.)