A trisection of A024495.

Terms

a(0) =0a(1) =6a(2) =42a(3) =342a(4) =2730a(5) =21846a(6) =174762a(7) =1398102a(8) =11184810a(9) =89478486a(10) =715827882a(11) =5726623062a(12) =45812984490a(13) =366503875926