Convolve natural numbers with characteristic function of triangular numbers.

Terms

a(0) =0a(1) =0a(2) =1a(3) =2a(4) =4a(5) =6a(6) =8a(7) =11a(8) =14a(9) =17a(10) =20a(11) =24a(12) =28a(13) =32a(14) =36a(15) =40a(16) =45a(17) =50a(18) =55a(19) =60a(20) =65a(21) =70a(22) =76a(23) =82a(24) =88a(25) =94a(26) =100a(27) =106a(28) =112a(29) =119