%I #5 Jun 11 2015 14:06:59
%S 1,3,18,144,1422,16848,235458,3827628,71466174,1515031920,36091609434,
%T 957367079244,28050237910926,901359663633000,31567805908329330,
%U 1198307340146774844,49060139971072916142,2156816501291429473248
%N Column 2 of triangle A123305.
%C Triangle T=A123305 is defined by: (column k of T) = (k+1)*(column k of T^2) shifted to have an initial '1'; thus this sequence shifted left equals 3 times column 2 of T^2 (matrix square of A123305).
%Y Cf. A123305, A123306, A123307, A123309, A123310, A123311.
%K nonn
%O 0,2
%A _Paul D. Hanna_, Sep 24 2006