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 A194718 Number of n-ary words beginning with the first character of the alphabet, that can be built by inserting six doublets into the initially empty word. 2
 0, 1, 462, 7941, 48838, 185193, 530526, 1265677, 2654646, 5060433, 8960878, 14964501, 23826342, 36463801, 53972478, 77642013, 108971926, 149687457, 201755406, 267399973, 349118598, 449697801, 572229022, 720124461, 897132918, 1107355633, 1355262126, 1645706037 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Alois P. Heinz, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (6, -15, 20, -15, 6, -1). FORMULA G.f.: x*(1+456*x+5184*x^2+8102*x^3+2055*x^4+42*x^5) / (x-1)^6. a(0) = 0, a(n) = 1+(10+(44+(110+(165+132*(n-1))*(n-1))*(n-1))*(n-1)) * (n-1) for n>0. EXAMPLE a(1) = 1: aaaaaaaaaaaa (with 1-ary alphabet {a}). MAPLE a:= n-> `if`(n=0, 0, (x-> 1+(10+(44+(110+(165+132*x)*x)*x)*x)*x)(n-1)): seq(a(n), n=0..30); MATHEMATICA LinearRecurrence[{6, -15, 20, -15, 6, -1}, {0, 1, 462, 7941, 48838, 185193, 530526}, 30] (* Harvey P. Dale, Oct 23 2015 *) CROSSREFS Row n=6 of A183134. Sequence in context: A236350 A027816 A027823 * A267283 A289349 A023912 Adjacent sequences:  A194715 A194716 A194717 * A194719 A194720 A194721 KEYWORD nonn AUTHOR Alois P. Heinz, Sep 02 2011 STATUS approved

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Last modified December 3 05:29 EST 2020. Contains 338899 sequences. (Running on oeis4.)