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A123781
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 and symmetric after a rotation by 180 degrees.
0
1, 1, 5, 7, 41, 65, 384, 649, 3853, 6745, 40209, 72334, 431188, 791144, 4717533, 8787824, 52396271, 98784645
OFFSET
1,3
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Søren Eilers, Oct 29 2006
EXTENSIONS
More terms by Søren Eilers, Sep 12 2018
STATUS
approved