-a(n)/7! is the coefficient of x^7 in the Taylor expansion of the k-th iteration of sin(x).

Terms

a(0) =0a(1) =1a(2) =128a(3) =731a(4) =2160a(5) =4765a(6) =8896a(7) =14903a(8) =23136a(9) =33945a(10) =47680a(11) =64691a(12) =85328a(13) =109941a(14) =138880a(15) =172495a(16) =211136a(17) =255153a(18) =304896a(19) =360715a(20) =422960a(21) =491981a(22) =568128a(23) =651751a(24) =743200a(25) =842825a(26) =950976a(27) =1068003a(28) =1194256a(29) =1330085