Triangular numbers containing 2n digits obtained by duplicating the first n digits; i.e., triangular numbers in A020338.

A068899

Triangular numbers containing 2n digits obtained by duplicating the first n digits; i.e., triangular numbers in A020338.

Terms

    a(0) =55a(1) =66a(2) =5050a(3) =5151a(4) =203203a(5) =255255a(6) =426426a(7) =500500a(8) =501501a(9) =581581a(10) =828828a(11) =930930a(12) =39653965a(13) =50005000a(14) =50015001a(15) =61566156a(16) =3347133471a(17) =5000050000a(18) =5000150001a(19) =6983669836a(20) =220028220028a(21) =500000500000a(22) =500001500001

External references