a(n) = Sum_{k=1..n} (2k-1)^(2k-1).A061787a(n) = Sum_{k=1..n} (2k-1)^(2k-1).Terms a(0) =1a(1) =28a(2) =3153a(3) =826696a(4) =388247185a(5) =285699917796External referencesoeis: A061787