A127716 a(n) = A127714(n, n*(n+1)/2).
1, 1, 3, 11, 72, 473, 3727, 39646, 412679, 4765654, 61015451, 937386045, 14126033578, 227901084348, 3941375013541, 72677938745613, 1517730017193292, 31249446089387086, 675658943143264102, 15356377683044270187
Offset: 0
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