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 A223687 Petersen graph (8,2) coloring a rectangular array: number of n X 3 0..15 arrays where 0..15 label nodes of a graph with edges 0,1 0,8 8,14 8,10 1,2 1,9 9,15 9,11 2,3 2,10 10,12 3,4 3,11 11,13 4,5 4,12 12,14 5,6 5,13 13,15 6,7 6,14 7,0 7,15 and every array movement to a horizontal or antidiagonal neighbor moves along an edge of this graph. 1
 144, 2304, 37008, 595584, 9594000, 154616832, 2492365968, 40180445568, 647800215696, 10444288589568, 168392298756240, 2714990519274624, 43773950520548496, 705771016545286656, 11379212680977220752 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Column 3 of A223692. LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 24*a(n-1) - 127*a(n-2). Conjectures from Colin Barker, Aug 22 2018: (Start) G.f.: 144*x*(1 - 8*x) / (1 - 24*x + 127*x^2). a(n) = (72*((12-sqrt(17))^n*(-31+8*sqrt(17)) + (12+sqrt(17))^n*(31+8*sqrt(17)))) / (127*sqrt(17)). (End) EXAMPLE Some solutions for n=3: .14..8.14...13..5..6...14..8.14...13.15..9....0..8.14....7.15..9....3.11.13 .10.12.14....6..5..6....0..8.10....9.15.13...14.12..4...13.15.13....3.11.13 .14..8..0....4..5..4...10..8.10...13.11..9....4..5.13...13.11..3...13.15..9 CROSSREFS Cf. A223692. Sequence in context: A008431 A250084 A280025 * A268625 A121344 A232819 Adjacent sequences: A223684 A223685 A223686 * A223688 A223689 A223690 KEYWORD nonn AUTHOR R. H. Hardin, Mar 25 2013 STATUS approved

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Last modified December 9 18:33 EST 2023. Contains 367693 sequences. (Running on oeis4.)