p-INVERT of the positive integers, where p(S) = (1 - S)(1 - S^2).

Terms

a(0) =1a(1) =4a(2) =13a(3) =39a(4) =114a(5) =330a(6) =948a(7) =2703a(8) =7655a(9) =21554a(10) =60389a(11) =168468a(12) =468199a(13) =1296826a(14) =3581185a(15) =9862749a(16) =27096216a(17) =74277342a(18) =203200986a(19) =554869701a(20) =1512575195a(21) =4116813032a(22) =11188568267a(23) =30367047720a(24) =82316338381a(25) =222875101936a(26) =602784607477