a(n) = p(7*n + 5), where p(k) = number of partitions of k = A000041(k).

Terms

a(0) =7a(1) =77a(2) =490a(3) =2436a(4) =10143a(5) =37338a(6) =124754a(7) =386155a(8) =1121505a(9) =3087735a(10) =8118264a(11) =20506255a(12) =49995925a(13) =118114304a(14) =271248950a(15) =607163746a(16) =1327710076a(17) =2841940500a(18) =5964539504a(19) =12292341831a(20) =24908858009a(21) =49686288421a(22) =97662728555a(23) =189334822579a(24) =362326859895a(25) =684957390936