Convolution of A010060 and A000244.

Terms

a(0) =0a(1) =1a(2) =4a(3) =12a(4) =37a(5) =111a(6) =333a(7) =1000a(8) =3001a(9) =9003a(10) =27009a(11) =81028a(12) =243084a(13) =729253a(14) =2187760a(15) =6563280a(16) =19689841a(17) =59069523a(18) =177208569a(19) =531625708a(20) =1594877124a(21) =4784631373a(22) =14353894120a(23) =43061682360a(24) =129185047080a(25) =387555141241