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A193519 a(n) = (2/3)*Sum_{i=1..n-1} A000129(i)*3^(n-i). 1
0, 0, 2, 10, 40, 144, 490, 1610, 5168, 16320, 50930, 157546, 484120, 1480080, 4507162, 13683050, 41439200, 125259264, 378051170, 1139641930, 3432176008, 10328516880, 31062778570, 93374780426, 280574458640, 842810055360, 2531053642322, 7599494558890, 22813774416760, 68478238362384 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Number of ternary words of length n on {0,1,2} containing the subwords 02 or 20. - Philippe Deléham, Apr 27 2012

REFERENCES

Gy. Tasi and F. Mizukami, Quantum algebraic-combinatoric study of the conformational properties of n-alkanes, J. Math. Chemistry, 25, 1999, 55-64 (see Eq. (19))).

LINKS

Table of n, a(n) for n=0..29.

Index entries for linear recurrences with constant coefficients, signature (5,-5,-3).

FORMULA

G.f.: 2x^2/(1-5*x+5*x^2+3*x^3). - Philippe Deléham, Apr 27 2012

a(n) = 5*a(n-1) - 5*a(n-2) - 3*a(n-3), a(0) = a(1) = 0, a(2) = 2. - Philippe Deléham, Apr 27 2012

EXAMPLE

a(3) = 10 because among the 3^3 = 27 ternary words of length 3 only 10, namely 002, 020, 021, 022, 102, 120, 200, 201, 202, 220 contain the subwords 02 or 20. - Philippe Deléham, Apr 27 2012

CROSSREFS

Equals twice A137212.

Sequence in context: A261473 A174395 A320526 * A268329 A223095 A052978

Adjacent sequences:  A193516 A193517 A193518 * A193520 A193521 A193522

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane, Jul 29 2011

STATUS

approved

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Last modified April 13 20:46 EDT 2021. Contains 342941 sequences. (Running on oeis4.)