T(n,k) is the number of 4-ary strings of length n+1 with k+1 indispensable digits and a nonzero leading digit with 0 <= k <= n.

A340620

T(n,k) is the number of 4-ary strings of length n+1 with k+1 indispensable digits and a nonzero leading digit with 0 <= k <= n.

Terms

    a(0) =3a(1) =6a(2) =6a(3) =10a(4) =28a(5) =10a(6) =15a(7) =81a(8) =81a(9) =15a(10) =21a(11) =186a(12) =354a(13) =186a(14) =21a(15) =28a(16) =371a(17) =1137a(18) =1137a(19) =371a(20) =28a(21) =36a(22) =672a(23) =3018a(24) =4836a(25) =3018a(26) =672a(27) =36a(28) =45a(29) =1134

External references