4999950000

Appears in sequences

• a(n) = 10^n*(10^n-1)/2.at n=5A037182
• Images of hexamorphic numbers: suppose k-th hexagonal number H(k) (A000384) ends in k; sequence gives positive values of H(k).at n=21A038494
• 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.at n=23A068812
• Triangular numbers obtained as the concatenation of n and n+1.at n=18A226788
• Kaprekar numbers that are the concatenation of two consecutive numbers.at n=15A381918
• Kaprekar numbers (A006886) that are divisible by the sum of their digits.at n=40A382165