a(n) is the smallest number m such that 2*k*m - 1 is composite for all k, 0 < k < n+1.

Terms

a(0) =5a(1) =13a(2) =13a(3) =62a(4) =73a(5) =73a(6) =89a(7) =118a(8) =118a(9) =118a(10) =118a(11) =118a(12) =236a(13) =926a(14) =959a(15) =959a(16) =959a(17) =959a(18) =959a(19) =959a(20) =1063a(21) =1474a(22) =1474a(23) =1474a(24) =1667a(25) =1667a(26) =6118a(27) =8249a(28) =9098a(29) =9098