Irregular triangle: row n is 1, 2, 3, 4, .., prime(n).

Terms

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