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A123818 Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 2 X 2. 0
1, 3, 31, 412, 6435, 106108, 1825803, 32320892, 584956651, 10772558067, 201219520632 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..11.

S. Eilers, The LEGO counting problem, Amer. Math. Mnthly, 123 (May 2016), 415-426.

Index entry for sequences related to LEGO blocks

CROSSREFS

Cf. A112389, A123762-A123827, A123829-A123849.

Sequence in context: A136596 A186207 A014178 * A087591 A061053 A047798

Adjacent sequences:  A123815 A123816 A123817 * A123819 A123820 A123821

KEYWORD

nonn,hard,more

AUTHOR

Søren Eilers, Oct 29 2006

STATUS

approved

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Last modified August 15 15:15 EDT 2022. Contains 356146 sequences. (Running on oeis4.)