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 A123189 a(1)=1; a(2)=1; a(3)=6; a(n)=3a(n-1)+3a(n-2)-4a(n-3) for n >=4. 0
 1, 1, 6, 17, 65, 222, 793, 2785, 9846, 34721, 122561, 432462, 1526185, 5385697, 19005798, 67069745, 236683841, 835237566, 2947485241, 10401433057, 36705804630, 129531772097, 457106997953, 1613093091630, 5692473180361 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS MAPLE a[1]:=1: a[2]:=1: a[3]:=6: for n from 4 to 25 do a[n]:=3*a[n-1]+3*a[n-2]-4*a[n-3] od: seq(a[n], n=1..25); MATHEMATICA M = {{1, -2, 1}, {-2, 2, 0}, {1, 1, 0}} v[1] = {1, 0, 0} v[n_] := v[n] = M.v[n - 1]; a1 = Table[v[n][[1]], {n, 1, 50}] CROSSREFS Sequence in context: A151350 A195741 A006758 * A219847 A047156 A128243 Adjacent sequences:  A123186 A123187 A123188 * A123190 A123191 A123192 KEYWORD nonn AUTHOR Roger L. Bagula, Oct 03 2006 EXTENSIONS Edited by N. J. A. Sloane, Oct 08 2006 STATUS approved

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Last modified June 18 08:40 EDT 2021. Contains 345098 sequences. (Running on oeis4.)