Number of n-member subsets of 1..2n whose elements sum to a multiple of n.

Terms

a(0) =1a(1) =2a(2) =2a(3) =8a(4) =18a(5) =52a(6) =152a(7) =492a(8) =1618a(9) =5408a(10) =18452a(11) =64132a(12) =225432a(13) =800048a(14) =2865228a(15) =10341208a(16) =37568338a(17) =137270956a(18) =504171584a(19) =1860277044a(20) =6892335668a(21) =25631327688a(22) =95640829924a(23) =357975249028