

A123764


Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 1 X 2 which is flat, i.e., with all blocks in parallel position.


0



1, 2, 7, 24, 99, 416, 1854, 8407, 38970, 182742, 866442, 4140607, 19925401, 96430625, 469005432, 2290860538, 11232074043, 55255074216, 272634835875
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OFFSET

1,2


REFERENCES

S. Eilers, The LEGO counting problem, Amer. Math. Mnthly, 123 (May 2016), 415426.


LINKS

Table of n, a(n) for n=1..19.
M. Abrahamsen and S. Eilers, On the asymptotic enumeration of LEGO structures, Exper Math. 20 (2) (2011) 145152.
B. Durhuus and S. Eilers, On the entropy of LEGO, arXiv:math/0504039 [math.CO], 2005.
S. Eilers, A LEGO Counting problem, 2005.
Index entry for sequences related to LEGO blocks


CROSSREFS

Sequence in context: A150436 A197553 A213950 * A150437 A150438 A150439
Adjacent sequences: A123761 A123762 A123763 * A123765 A123766 A123767


KEYWORD

nonn,hard


AUTHOR

Søren Eilers, Oct 29 2006


STATUS

approved



