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 A233807 Number of tilings of an n X n square using right trominoes and at most one monomino. 5
 1, 1, 4, 0, 16, 128, 162, 34528, 943096, 1193600, 3525377600, 480585761344, 2033502499954, 46983507796973152, 32908187880881958736, 458324092996867592192, 83153202122213272708832688, 299769486068040749617049301344 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Wikipedia, Tromino EXAMPLE a(2) = 4: .___.  .___.  .___.  .___. |_| |  | |_|  | ._|  |_. | |___|  |___|  |_|_|  |_|_|. MAPLE b:= proc(n, w, l) option remember; local k, t;       if max(l[])>n then 0 elif n=0 then 1     elif min(l[])>0 then t:=min(l[]); b(n-t, w, map(h->h-t, l))     else for k while l[k]>0 do od;          `if`(w, b(n, false, s(k=1, l)), 0)+          `if`(k>1 and l[k-1]=1, b(n, w, s(k=2, k-1=2, l)), 0)+          `if`(k b(n, evalb(irem(n, 3)>0), [0\$n]): s:= subsop: seq(a(n), n=0..10); MATHEMATICA \$RecursionLimit = 1000; s = ReplacePart; b[n_, w_, l_] := b[n, w, l] = Module[{k, t}, Which[Max[l] > n, 0, n == 0, 1, Min[l] > 0, t = Min[l]; b[n-t, w, l-t], True, For[k = 1, l[[k]] > 0, k++ ]; If[w, b[n, False, s[l, k -> 1]], 0]+If[k > 1 && l[[k-1]] == 1, b[n, w, s[l, {k -> 2, k-1 -> 2}]], 0] + If[k < Length[l] && l[[k+1]] == 1, b[n, w, s[l, {k -> 2, k+1 -> 2}]], 0] + If[k < Length[l] && l[[k+1]] == 0, b[n, w, s[l, {k -> 1, k+1 -> 2}]]+b[n, w, s[l, {k -> 2, k+1 -> 1}]] + If[w, b[n, False, s[l, {k -> 2, k+1 -> 2}]], 0], 0] + If[k+1 < Length[l] && l[[k+1]] == 0 && l[[k+2]] == 0, b[n, w, s[l, {k -> 2, k+1 -> 2, k+2 -> 2}]], 0] ] ]; a[n_] := b[n, Mod[n, 3] > 0, Array[0 &, n]]; Table[Print[an = a[n]]; an, {n, 0, 16}] (* Jean-François Alcover, Dec 30 2013, translated from Maple *) CROSSREFS Cf. A000105, A219874, A219952, A219975, A219994, A220061. Sequence in context: A247120 A002979 A137279 * A302771 A167350 A215669 Adjacent sequences:  A233804 A233805 A233806 * A233808 A233809 A233810 KEYWORD nonn AUTHOR Alois P. Heinz, Dec 16 2013 EXTENSIONS a(17) from Alois P. Heinz, Sep 24 2014 STATUS approved

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Last modified April 10 08:09 EDT 2021. Contains 342845 sequences. (Running on oeis4.)