First differences of A227693.

Terms

a(0) =3a(1) =21a(2) =143a(3) =1061a(4) =8366a(5) =68932a(6) =585881a(7) =5094722a(8) =45074595a(9) =404185377a(10) =3663479699a(11) =33498077106a(12) =308548877876