Greatest minimal norm of sublattice of index n in hexagonal lattice.

Terms

a(0) =1a(1) =1a(2) =3a(3) =4a(4) =3a(5) =4a(6) =7a(7) =7a(8) =9a(9) =7a(10) =7a(11) =12a(12) =13a(13) =12a(14) =13a(15) =16a(16) =13a(17) =13a(18) =19a(19) =16a(20) =21a(21) =19a(22) =19a(23) =21a(24) =25a(25) =21a(26) =27a(27) =28a(28) =21a(29) =27