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A229915 Number of espalier polycubes of a given volume in dimension 3. 5
1, 3, 5, 10, 14, 26, 34, 57, 76, 116, 150, 227, 284, 408, 520, 718, 895, 1226, 1508, 2018, 2487, 3248, 3968, 5160, 6235, 7970, 9653, 12179, 14630, 18367, 21924, 27241, 32506, 39985, 47492, 58203, 68752, 83613, 98730, 119269, 140224, 168799, 197758, 236753, 277052, 329867, 384852, 457006, 531500, 628338 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

A pyramid polycube is obtained by gluing together horizontal plateaux (parallelepipeds of height 1) in such a way that (0,0,0) belongs to the first plateau and each cell with coordinate (0,b,c) belonging to the first plateau is such that b , c >= 0. If the cell with coordinates (a,b,c) belongs to the (a+1)-st plateau (a>0), then the cell with coordinates (a-1, b, c) belongs to the a-th plateau.

An espalier polycube is a special pyramid such that each plateau contains the cell with coordinate (a,0,0).

REFERENCES

C. Carré, N. Debroux, M. Deneufchatel, J.-P. Dubernard et al., Dirichlet convolution and enumeration of pyramid polycubes, 2013; http://hal.archives-ouvertes.fr/docs/00/90/58/89/PDF/polycubes.pdf

LINKS

Table of n, a(n) for n=1..50.

FORMULA

The generating function for the numbers of espaliers of height h and volumes v_1 , ... v_h is x_1^{n_1} * ... x_h^{n_h} / ((1-x_1^{n_1}) *(1-x_1^{n_1}*x_2^{n_2}) *... *(1-x_1^{n_1}*x_2^{n_2}*...x_h^{n_h})).

This sequence is obtained with x_1 = ... = x_h = p by summing over n_1>= ... >= n_h>=1 and then over h.

CROSSREFS

Cf. A227925, A230118, A229917, A229925.

Sequence in context: A078411 A137630 A220489 * A092269 A182722 A089483

Adjacent sequences:  A229912 A229913 A229914 * A229916 A229917 A229918

KEYWORD

nonn

AUTHOR

Matthieu Deneufchâtel, Oct 03 2013

STATUS

approved

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Last modified November 20 13:59 EST 2017. Contains 294972 sequences.