Number of compositions of 7*n into parts 3 and 7.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =9a(5) =37a(6) =122a(7) =346a(8) =913a(9) =2398a(10) =6515a(11) =18317a(12) =52226a(13) =148408a(14) =417810a(15) =1168085a(16) =3258813a(17) =9103828a(18) =25488736a(19) =71462437a(20) =200406479a(21) =561770980a(22) =1573939555a(23) =4408629727a(24) =12348599802a(25) =34592601763a(26) =96916209910a(27) =271537125048a(28) =760777555986