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 A270258 Number of 3X3X3 triangular 0..n arrays with some element plus some adjacent element totalling n exactly once. 1
 0, 66, 768, 4428, 14976, 42750, 96768, 203448, 376320, 668250, 1094400, 1746756, 2636928, 3910998, 5569536, 7830000, 10672128, 14404338, 18973440, 24800700, 31785600, 40486446, 50738688, 63264168, 77815296, 95306250, 115385088 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Row 3 of A270256. LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 2*a(n-1) +3*a(n-2) -8*a(n-3) -2*a(n-4) +12*a(n-5) -2*a(n-6) -8*a(n-7) +3*a(n-8) +2*a(n-9) -a(n-10) Empirical for n mod 2 = 0: a(n) = 9*n^5 - 27*n^4 + 42*n^3 - 39*n^2 + 15*n Empirical for n mod 2 = 1: a(n) = 9*n^5 - 27*n^4 + 30*n^3 + 6*n^2 - 39*n + 21 EXAMPLE Some solutions for n=4 ....3......2......2......0......2......1......0......2......4......4......3 ...2.2....1.4....0.3....1.0....1.3....3.0....3.2....0.3....1.3....2.3....4.4 ..3.3.3..4.1.3..4.2.3..4.4.2..4.4.2..0.3.3..0.4.3..2.2.3..1.4.4..1.2.4..2.3.1 CROSSREFS Cf. A270256. Sequence in context: A046409 A128952 A282050 * A223410 A258917 A223152 Adjacent sequences:  A270255 A270256 A270257 * A270259 A270260 A270261 KEYWORD nonn AUTHOR R. H. Hardin, Mar 14 2016 STATUS approved

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Last modified December 7 16:53 EST 2021. Contains 349581 sequences. (Running on oeis4.)