Triangle Triples
April 01, 2012
| Let T(n) be the nth triangle number, so T(n) = |
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Let dT(n) be the number of divisors of T(n). E.g.: T(7) = 28 and dT(7) = 6.
Let Tr(n) be the number of triples (i, j, k) such that 1 ≤ i < j < k ≤ n and dT(i) > dT(j) > dT(k). Tr(20) = 14, Tr(100) = 5772 and Tr(1000) = 11174776.
Find Tr(60 000 000). Give the last 18 digits of your answer.
Written by gamwe6 who lives and works in San Francisco building useful things. You should follow him on Twitter