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A062202
Number of compositions of n such that two adjacent parts are not equal modulo 4.
2
1, 1, 1, 3, 4, 7, 12, 22, 33, 57, 103, 169, 277, 479, 824, 1368, 2306, 3941, 6657, 11206, 18998, 32194, 54325, 91880, 155633, 263120, 444674, 752545, 1273278, 2152704, 3640801, 6159723, 10418147, 17618849, 29802480, 50410743, 85259765
OFFSET
0,4
REFERENCES
I. P. Goulden and D. M. Jackson, Combinatorial Enumeration, Wiley, N.Y., 1983,(Problem 2.4.13).
FORMULA
G.f.: -(x^4-x-1)*(x^4-x^2-1)*(x^4-x^3-1)/(x^16-x^15-x^14-3*x^12+3*x^11+x^10+2*x^9+6*x^8-x^7-3*x^6-2*x^5-5*x^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)).
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladeta Jovovic, Jun 13 2001
STATUS
approved