Number of Schur rings over Z_{7^n}.

Terms

a(0) =1a(1) =4a(2) =21a(3) =113a(4) =614a(5) =3351a(6) =18329a(7) =100372a(8) =550009a(9) =3015021a(10) =16531326a(11) =90653323a(12) =497159809a(13) =2726660260a(14) =14954795741a(15) =82023673921a(16) =449887538266