Number of nonsplit type 2 metacyclic 2-groups of order 2^n.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =0a(7) =1a(8) =2a(9) =4a(10) =6a(11) =10a(12) =13a(13) =19a(14) =24a(15) =32a(16) =39a(17) =50a(18) =59a(19) =73a(20) =85a(21) =102a(22) =117a(23) =138a(24) =156a(25) =181a(26) =203a(27) =232a(28) =258a(29) =292