Triangular array starting with {1,1}; then i-th term in a row gives number of i's in next row.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =1a(5) =2a(6) =2a(7) =1a(8) =2a(9) =2a(10) =3a(11) =3a(12) =1a(13) =2a(14) =2a(15) =3a(16) =3a(17) =4a(18) =4a(19) =4a(20) =5a(21) =5a(22) =5a(23) =1a(24) =2a(25) =2a(26) =3a(27) =3a(28) =4a(29) =4