Number of unordered pairs of distinct length-n binary words having the same number of 1's.

A108958

Number of unordered pairs of distinct length-n binary words having the same number of 1's.

Terms

    a(0) =0a(1) =1a(2) =6a(3) =27a(4) =110a(5) =430a(6) =1652a(7) =6307a(8) =24054a(9) =91866a(10) =351692a(11) =1350030a(12) =5196204a(13) =20050108a(14) =77542376a(15) =300507427a(16) =1166737574a(17) =4537436578a(18) =17672369756a(19) =68922740122a(20) =269127888644

External references