A123308 Column 2 of triangle A123305.

1, 3, 18, 144, 1422, 16848, 235458, 3827628, 71466174, 1515031920, 36091609434, 957367079244, 28050237910926, 901359663633000, 31567805908329330, 1198307340146774844, 49060139971072916142, 2156816501291429473248

Offset: 0

Author

Paul D. Hanna, Sep 24 2006

Keywords

• nonn

Comments

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).

Crossrefs

Cf. A123305, A123306, A123307, A123309, A123310, A123311.