Triangular numbers whose external digits form a triangular number. Or triangular number whose MSD and LSD form a triangular number.
A077367
Triangular numbers whose external digits form a triangular number. Or triangular number whose MSD and LSD form a triangular number.
Terms
- a(0) =0a(1) =1a(2) =3a(3) =6a(4) =10a(5) =15a(6) =21a(7) =28a(8) =36a(9) =45a(10) =55a(11) =66a(12) =78a(13) =91a(14) =105a(15) =120a(16) =190a(17) =231a(18) =435a(19) =465a(20) =595a(21) =666a(22) =1035a(23) =1225a(24) =1275a(25) =1485a(26) =1540a(27) =1770a(28) =1830a(29) =2211
External references
- oeis: A077367