a(n) = (29^n - 1)/28.A218732a(n) = (29^n - 1)/28.Terms a(0) =0a(1) =1a(2) =30a(3) =871a(4) =25260a(5) =732541a(6) =21243690a(7) =616067011a(8) =17865943320a(9) =518112356281External referencesoeis: A218732