First differences of A047835.

Terms

a(0) =0a(1) =0a(2) =1a(3) =69a(4) =1694a(5) =22932a(6) =208152a(7) =1413720a(8) =7697052a(9) =35194302a(10) =139687119a(11) =493127635a(12) =1577331756a(13) =4637757488a(14) =12679063488a(15) =32529562560a(16) =78917794128a(17) =182184724908a(18) =402332471541a(19) =853769650041