a(n) = (n^(2n) - (n-1)^(2n))/(2n-1).A280305a(n) = (n^(2n) - (n-1)^(2n))/(2n-1).Terms a(0) =1a(1) =5a(2) =133a(3) =8425a(4) =968561a(5) =175694701a(6) =46142992981External referencesoeis: A280305