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A106353
Number of compositions of n into 4 parts such that no two adjacent parts are equal.
1
2, 6, 14, 24, 46, 66, 100, 138, 192, 246, 324, 402, 506, 612, 746, 882, 1054, 1224, 1432, 1644, 1896, 2148, 2448, 2748, 3098, 3450, 3854, 4260, 4726, 5190, 5716, 6246, 6840, 7434, 8100, 8766, 9506, 10248, 11066, 11886, 12790, 13692, 14680, 15672
OFFSET
6,1
LINKS
A. Knopfmacher and H. Prodinger, On Carlitz compositions, European Journal of Combinatorics, Vol. 19, 1998, pp. 579-589.
Index entries for linear recurrences with constant coefficients, signature (1, 1, 0, 0, -2, 0, 0, 1, 1, -1).
FORMULA
G.f.: (8*x^10+4*x^9+6*x^8+4*x^7+2*x^6) / ((1-x)*(1-x^2)*(1-x^3)*(1-x^4)).
MATHEMATICA
Drop[CoefficientList[Series[(8x^10+4x^9+6x^8+4x^7+2x^6)/((1-x)(1-x^2)(1-x^3)(1-x^4)), {x, 0, 60}], x], 6] (* or *) LinearRecurrence[{1, 1, 0, 0, -2, 0, 0, 1, 1, -1}, {2, 6, 14, 24, 46, 66, 100, 138, 192, 246}, 60] (* Harvey P. Dale, Apr 02 2023 *)
CROSSREFS
Column 4 of A106351. Cf. A003242.
Sequence in context: A109592 A238410 A256482 * A002703 A230978 A112853
KEYWORD
nonn
AUTHOR
Christian G. Bower, Apr 29 2005
STATUS
approved