1999000

Appears in sequences

• Numbers k such that k = T(x) + T(y) where T(m) is the m-th triangular number and k is concatenate(x, y) in base 10.at n=10A113796
• Triangular numbers composed of digits {0,1,9}.at n=11A119047
• Numbers m such that m = Sum_{i=x..y} i = (10^k)*y + x, where 0 <= x < y, 0 <= x < 10^k for some positive integers k.at n=9A186076