Define a(1)=0, a(2)=0, a(3)=15, a(4)=111 then a(n) = 254*a(n-2) - a(n-4) + 126 also sequence such that 7*a(n)*(a(n) + 1) + 1 = a square.

A105051

Define a(1)=0, a(2)=0, a(3)=15, a(4)=111 then a(n) = 254*a(n-2) - a(n-4) + 126 also sequence such that 7*a(n)*(a(n) + 1) + 1 = a square.