

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
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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 (a1, b, c) belongs to the ath 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.archivesouvertes.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} / ((1x_1^{n_1}) *(1x_1^{n_1}*x_2^{n_2}) *... *(1x_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



