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 A233505 Number of tilings of a 2 X 2 X n box using bricks of shape 3 X 1 X 1 and 2 X 1 X 1. 5
 1, 2, 9, 45, 201, 1062, 5564, 28859, 152012, 799387, 4202165, 22117465, 116385352, 612443308, 3223118545, 16961953022, 89264218645, 469766599585, 2472212575433, 13010374123502, 68468999197712, 360328057238019, 1896278913278432, 9979444454056631 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Alois P. Heinz, Table of n, a(n) for n = 0..1000 FORMULA G.f.: (x^17 +3*x^16 -x^15 -5*x^14 +8*x^13 -8*x^12 -22*x^10 -20*x^9 -62*x^8 -20*x^7 -42*x^6 +18*x^5 +19*x^3 +x^2 +3*x -1) / (-x^20 -2*x^19 +2*x^18 +9*x^17 -12*x^16 +27*x^15 +41*x^14 +66*x^13 +62*x^12 +184*x^11 +76*x^10 +156*x^9 -92*x^8 +20*x^7 -141*x^6 +28*x^5 -62*x^4 +19*x^3 +5*x -1). MAPLE a:= n-> coeff(series((x^17 +3*x^16 -x^15 -5*x^14 +8*x^13 -8*x^12 -22*x^10 -20*x^9 -62*x^8 -20*x^7 -42*x^6 +18*x^5 +19*x^3 +x^2 +3*x -1)/(-x^20 -2*x^19 +2*x^18 +9*x^17 -12*x^16 +27*x^15 +41*x^14 +66*x^13 +62*x^12 +184*x^11 +76*x^10 +156*x^9 -92*x^8 +20*x^7 -141*x^6 +28*x^5 -62*x^4 +19*x^3 +5*x -1), x, n+1), x, n): seq(a(n), n=0..40); CROSSREFS Cf. A000931, A129682, A219866, A219867, A233313, A233506, A233507, A233509. Sequence in context: A059392 A264111 A264122 * A228767 A074607 A251178 Adjacent sequences: A233502 A233503 A233504 * A233506 A233507 A233508 KEYWORD nonn,easy AUTHOR Alois P. Heinz, Dec 11 2013 STATUS approved

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Last modified February 6 23:12 EST 2023. Contains 360111 sequences. (Running on oeis4.)