Sophie Germain triangular numbers tr: 2*tr+1 is also a triangular number.

A124174

Sophie Germain triangular numbers tr: 2*tr+1 is also a triangular number.

Terms

    a(0) =0a(1) =1a(2) =10a(3) =45a(4) =351a(5) =1540a(6) =11935a(7) =52326a(8) =405450a(9) =1777555a(10) =13773376a(11) =60384555a(12) =467889345a(13) =2051297326a(14) =15894464365a(15) =69683724540a(16) =539943899076

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