Triangular numbers m such that A040115(m) is also triangular.

Terms

a(0) =0a(1) =1a(2) =3a(3) =6a(4) =10a(5) =21a(6) =28a(7) =36a(8) =45a(9) =55a(10) =66a(11) =78a(12) =105a(13) =171a(14) =465a(15) =528a(16) =561a(17) =666a(18) =2211a(19) =4465a(20) =7503a(21) =16836a(22) =18336a(23) =22791a(24) =44850a(25) =53628a(26) =55278a(27) =82621a(28) =105111a(29) =114003