Triangular numbers of the form k^2 + k - 1.

A217758

Triangular numbers of the form k^2 + k - 1.

Terms

    a(0) =1a(1) =55a(2) =1891a(3) =64261a(4) =2183005a(5) =74157931a(6) =2519186671a(7) =85578188905

External references