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 A171761 Number of ternary squareful words of length n. 0
 0, 0, 3, 15, 63, 213, 687, 2127, 6483, 19575, 58905, 176943, 531177, 1593981, 4782513, 14348289, 43045923, 129139119, 387419097, 1162259637, 3486782013, 10460350023, 31381055463, 94143173409 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS FORMULA a(n) = A000244(n) - A006156(n). MATHEMATICA nmax = 23; 3^Range[0, nmax] - Length /@ NestList[ DeleteCases[ Flatten[ Outer[ Append, #, {1, 2, 3}, 1], 1], {___, x__, x__, ___}] &, {{}}, nmax] (* Jean-François Alcover, Jun 12 2017, using Vladimir Reshetnikov's code for A006156 *) CROSSREFS Cf. A000244, A006156. Sequence in context: A062211 A260326 A204086 * A229277 A218313 A218190 Adjacent sequences: A171758 A171759 A171760 * A171762 A171763 A171764 KEYWORD nonn AUTHOR Mats Granvik, Dec 18 2009 STATUS approved

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Last modified February 7 08:50 EST 2023. Contains 360115 sequences. (Running on oeis4.)