Triangular numbers in which the sum of the external digits equals the sum of the internal digits.

Terms

a(0) =231a(1) =253a(2) =561a(3) =990a(4) =2211a(5) =4095a(6) =5050a(7) =5151a(8) =6903a(9) =9180a(10) =11325a(11) =11628a(12) =20301a(13) =20503a(14) =31626a(15) =41041a(16) =51040a(17) =53301a(18) =63546a(19) =66066a(20) =67528a(21) =76245a(22) =92665a(23) =95703a(24) =97020a(25) =98346a(26) =99235a(27) =130305a(28) =131328a(29) =161028