Place where n-th 1 occurs in A023131.

Terms

a(0) =1a(1) =4a(2) =10a(3) =19a(4) =31a(5) =46a(6) =63a(7) =83a(8) =106a(9) =132a(10) =161a(11) =193a(12) =227a(13) =264a(14) =304a(15) =347a(16) =393a(17) =442a(18) =493a(19) =547a(20) =604a(21) =664a(22) =727a(23) =793a(24) =861a(25) =932a(26) =1006a(27) =1083a(28) =1163a(29) =1246