Triangular numbers for which the sum of the digits is a pentagonal number.

Terms

a(0) =0a(1) =1a(2) =10a(3) =66a(4) =435a(5) =561a(6) =741a(7) =903a(8) =1128a(9) =1326a(10) =1830a(11) =2145a(12) =2415a(13) =3081a(14) =5151a(15) =6105a(16) =7140a(17) =10731a(18) =11325a(19) =12090a(20) =12720a(21) =13530a(22) =15051a(23) =19110a(24) =20910a(25) =30135a(26) =31125a(27) =33411a(28) =50403a(29) =53301