Truncated triangular numbers (of form n*(n-3)/2 - k^2+k*n+1 for 1<=k<n).

Terms

a(0) =1a(1) =3a(2) =6a(3) =7a(4) =10a(5) =12a(6) =15a(7) =18a(8) =19a(9) =21a(10) =25a(11) =27a(12) =28a(13) =33a(14) =36a(15) =37a(16) =42a(17) =45a(18) =46a(19) =48a(20) =52a(21) =55a(22) =57a(23) =60a(24) =61a(25) =63a(26) =66a(27) =69a(28) =73a(29) =75