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 A264551 Number of (2+1) X (n+1) arrays of permutations of 0..n*3+2 with each element having directed index change -1,1 -1,2 1,0 or 0,-1. 1
 1, 2, 6, 16, 40, 96, 240, 608, 1536, 3840, 9600, 24064, 60416, 151552, 379904, 952320, 2387968, 5988352, 15015936, 37650432, 94404608, 236716032, 593559552, 1488322560, 3731881984, 9357492224, 23463460864, 58833502208, 147522060288 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 2*a(n-1) + 8*a(n-4). Empirical g.f.: x*(1 + 2*x^2 + 4*x^3) / (1 - 2*x - 8*x^4). - Colin Barker, Jan 08 2019 EXAMPLE Some solutions for n=4: ..1..2..6..4..8....1..5..3..4..8....1..5..3..7..8....1..2..5..4..8 ..0.10.11..3.13....0.10..2.12.13....0.10..2.12..4....0..7.10..3.12 ..5.12..7.14..9...11..6..7.14..9...11..6.13.14..9...11..6.13.14..9 CROSSREFS Row 2 of A264550. Sequence in context: A129952 A057711 A302239 * A293004 A265278 A111281 Adjacent sequences:  A264548 A264549 A264550 * A264552 A264553 A264554 KEYWORD nonn AUTHOR R. H. Hardin, Nov 17 2015 STATUS approved

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Last modified September 18 23:16 EDT 2021. Contains 347548 sequences. (Running on oeis4.)