Position of n-th 0 in A031087.

Terms

a(0) =0a(1) =9a(2) =27a(3) =45a(4) =63a(5) =81a(6) =99a(7) =117a(8) =135a(9) =153a(10) =154a(11) =157a(12) =160a(13) =163a(14) =166a(15) =169a(16) =172a(17) =175a(18) =178a(19) =180a(20) =207a(21) =234a(22) =261a(23) =288a(24) =315a(25) =342a(26) =369a(27) =396a(28) =397a(29) =400