a(n) = (40^n - 1)/39.A218743a(n) = (40^n - 1)/39.Terms a(0) =0a(1) =1a(2) =41a(3) =1641a(4) =65641a(5) =2625641a(6) =105025641a(7) =4201025641a(8) =168041025641External referencesoeis: A218743