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A276031 Number of edges in the graded poset of the partitions of n taken modulo 3, where a partition into k parts is joined to a partition into k+1 parts if the latter is a refinement of the former. 1
0, 1, 2, 5, 9, 14, 21, 30, 41, 54, 70, 89, 110, 135, 164, 195, 231, 272, 315, 364, 419, 476, 540, 611, 684, 765, 854, 945, 1045, 1154, 1265, 1386, 1517, 1650, 1794, 1949, 2106, 2275, 2456, 2639, 2835, 3044, 3255, 3480, 3719, 3960, 4216, 4487, 4760, 5049, 5354 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..10000

FORMULA

G.f.: (x^6-2*x^5+x^4-x^3+2*x^2+1)*x^2/((x^2+x+1)^2*(x-1)^4). - Alois P. Heinz, Aug 27 2016

EXAMPLE

a(6) = 14, the 14 edges are:  (111111) - (21111), (21111) - (1110), (21111) - (2211), (1110) - (111), (1110) - (210), (2211) - (111), (2211) - (210), (2211) - (222), (210) - (00), (210) - (21), (111) - (21), (222) - (21), (00) - (0), (21) - (0).

CROSSREFS

Cf. A000097, A140144.

Sequence in context: A152888 A139423 A026053 * A011905 A306674 A098065

Adjacent sequences:  A276028 A276029 A276030 * A276032 A276033 A276034

KEYWORD

nonn

AUTHOR

Caleb Ji, Aug 17 2016

EXTENSIONS

More terms from Alois P. Heinz, Aug 27 2016

STATUS

approved

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Last modified May 28 21:37 EDT 2020. Contains 334690 sequences. (Running on oeis4.)