A272686 Second differences of A078482.
0, 3, 10, 36, 134, 510, 1976, 7770, 30934, 124456, 505254, 2067250, 8516028, 35292978, 147045490, 615572172, 2587970166, 10922249958, 46257477232, 196532215226, 837432161710, 3577882539792, 15323984114822, 65781749593002, 282979540332660
Offset: 0