A modified Legendre-binomial transform of 4^n for p=3.

Terms

a(0) =1a(1) =3a(2) =21a(3) =63a(4) =189a(5) =1323a(6) =4161a(7) =12483a(8) =87381a(9) =262143a(10) =786429a(11) =5505003a(12) =16515009a(13) =49545027a(14) =346815189a(15) =1090777023a(16) =3272331069a(17) =22906317483a(18) =68719738881a(19) =206159216643