Number of cubic residues mod 3^n.

Terms

a(0) =1a(1) =3a(2) =3a(3) =7a(4) =21a(5) =57a(6) =169a(7) =507a(8) =1515a(9) =4543a(10) =13629a(11) =40881a(12) =122641a(13) =367923a(14) =1103763a(15) =3311287a(16) =9933861a(17) =29801577a(18) =89404729a(19) =268214187a(20) =804642555a(21) =2413927663a(22) =7241782989a(23) =21725348961a(24) =65176046881a(25) =195528140643a(26) =586584421923