a(n) = p * 5^p - 1 where p=prime(n).A100690a(n) = p * 5^p - 1 where p=prime(n).Terms a(0) =49a(1) =374a(2) =15624a(3) =546874a(4) =537109374a(5) =15869140624External referencesoeis: A100690