A182642(n) - A107857(n-1) for n>=1.

Terms

a(0) =0a(1) =1a(2) =4a(3) =6a(4) =18a(5) =31a(6) =82a(7) =132a(8) =348a(9) =565a(10) =1480a(11) =2394a(12) =6270a(13) =10147a(14) =26566a(15) =42984a(16) =112536a(17) =182089a(18) =476716a(19) =771342a(20) =2019402a(21) =3267463a(22) =8554330a(23) =13841196a(24) =36236725a(25) =58632253a(26) =153501232a(27) =248370211a(28) =650241655