First differences of A137212.

Terms

a(0) =0a(1) =1a(2) =4a(3) =15a(4) =52a(5) =173a(6) =560a(7) =1779a(8) =5576a(9) =17305a(10) =53308a(11) =163287a(12) =497980a(13) =1513541a(14) =4587944a(15) =13878075a(16) =41910032a(17) =126395953a(18) =380795380a(19) =1146267039a(20) =3448170436a(21) =10367130845a(22) =31156000928a(23) =93599839107a(24) =281117798360a(25) =844121793481