Number of starters in cyclic group of order 2n+1.

Terms

a(0) =1a(1) =1a(2) =3a(3) =9a(4) =25a(5) =133a(6) =631a(7) =3857a(8) =25905a(9) =188181a(10) =1515283a(11) =13376125a(12) =128102625a(13) =1317606101a(14) =14534145947a(15) =170922533545