(2n)! * Sum[k=n..2n, 1/k].A101613(2n)! * Sum[k=n..2n, 1/k].Terms a(0) =3a(1) =26a(2) =684a(3) =35664a(4) =3068640a(5) =392722560a(6) =69878833920External referencesoeis: A101613