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A123780 Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 1 X 4 which is flat, i.e., with all blocks in parallel position. 0
1, 4, 33, 294, 2951, 30668, 328999, 3596934, 39932206, 448517488, 5086259884, 58135266335 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..12.

CROSSREFS

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

Sequence in context: A202765 A264830 A237872 * A054371 A028576 A093185

Adjacent sequences:  A123777 A123778 A123779 * A123781 A123782 A123783

KEYWORD

nonn,hard

AUTHOR

Søren Eilers, Oct 29 2006

STATUS

approved

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Last modified March 28 11:00 EDT 2020. Contains 333083 sequences. (Running on oeis4.)