The 3rd Witt transform of A000027.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =2a(5) =7a(6) =18a(7) =42a(8) =84a(9) =153a(10) =264a(11) =429a(12) =666a(13) =1001a(14) =1456a(15) =2061a(16) =2856a(17) =3876a(18) =5166a(19) =6783a(20) =8778a(21) =11214a(22) =14168a(23) =17710a(24) =21924a(25) =26910a(26) =32760a(27) =39582a(28) =47502a(29) =56637