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%I #4 May 10 2013 12:44:47
%S 1,1,1,3,4,5,13,17,23,54,75,106,224,329,482,942,1436,2163,4004,6255,
%T 9619,17144,27220,42513,73785,118402,187082,318715,514958,820744,
%U 1380185,2239747,3592811,5987313,9742606,15703097,26004453,42385083
%N Number of compositions of n such that two adjacent parts are not equal modulo 3.
%D I. P. Goulden and D. M. Jackson, Combinatorial Enumeration, Wiley, N.Y., 1983,(Problem 2.4.13).
%F G.f.: -(x^3-x-1)*(x^3-x^2-1)/(x^9-x^8-x^7-2*x^6+x^5+x^4+4*x^3-1). Generally, g.f. for the number of compositions of n such that two adjacent parts are not equal modulo p is 1/(1-Sum_{i=1..p} x^i/(1+x^i-x^p)).
%Y Cf. A003242, A062200-A062203.
%K nonn
%O 0,4
%A _Vladeta Jovovic_, Jun 13 2001