Number of matroids of rank 2 on n labeled points.

Terms

a(0) =0a(1) =0a(2) =1a(3) =7a(4) =36a(5) =171a(6) =813a(7) =4012a(8) =20891a(9) =115463a(10) =677546a(11) =4211549a(12) =27640341a(13) =190891130a(14) =1382942161a(15) =10480109379a(16) =82864804268a(17) =682076675087