110 people attended OEIS-50 (videos, suggestions); annual fundraising drive to start soon (donate); editors, please edit! (stack is over 300), your editing is more valuable than any donation.
%I
%S 1,2,4,13,45,293,1880,22810,274047,6160861,137419960,5755708030,
%T 238764714329,18607726818765,1436358552064865,208215628095796834,
%U 29898827223053355535,8063377147636346175953,2154023814255202610544411
%N Number of planar n X n X n binary triangular grids with mirror symmetry about one altitude with no more than 4 ones in any 3 X 3 X 3 subtriangle.
%K nonn
%O 0,2
%A _R. H. Hardin_ Jan 03 2009