Numbers n such that n and its 10's complement are both triangular numbers; that is, n and 10^k - n (where k is the number of digits in n) are triangular numbers.
A068812
Numbers n such that n and its 10's complement are both triangular numbers; that is, n and 10^k - n (where k is the number of digits in n) are triangular numbers.
Terms
- a(0) =45a(1) =55a(2) =990a(3) =1485a(4) =4005a(5) =4950a(6) =5050a(7) =5995a(8) =8515a(9) =9180a(10) =285390a(11) =499500a(12) =500500a(13) =714610a(14) =1719585a(15) =3064050a(16) =6935950a(17) =8280415a(18) =49000050a(19) =49995000a(20) =50005000a(21) =50999950a(22) =1449668935a(23) =4999950000a(24) =5000050000a(25) =8550331065a(26) =122307408405a(27) =122963116095
External references
- oeis: A068812