Indices of triangular numbers listed in A075088.

Terms

a(0) =1a(1) =2a(2) =3a(3) =7a(4) =8a(5) =15a(6) =32a(7) =64a(8) =63a(9) =224a(10) =255a(11) =1280a(12) =512a(13) =3968a(14) =6399a(15) =10240a(16) =4095a(17) =14336a(18) =32768a(19) =65535a(20) =229375a(21) =180224a(22) =483327a(23) =262143a(24) =2097151a(25) =1048575a(26) =14680064a(27) =17432576a(28) =33554432a(29) =67108864