Triangle T(n,k) = Sum_{d|n} phi(d)*k^(n/d).

Terms

a(0) =1a(1) =2a(2) =6a(3) =3a(4) =12a(5) =33a(6) =4a(7) =24a(8) =96a(9) =280a(10) =5a(11) =40a(12) =255a(13) =1040a(14) =3145a(15) =6a(16) =84a(17) =780a(18) =4200a(19) =15810a(20) =46956a(21) =7a(22) =140a(23) =2205a(24) =16408a(25) =78155a(26) =279972a(27) =823585a(28) =8a(29) =288