a(n) is the least multiple of n which uses only digit 2, or a(n) = -1 if no such multiple exists.

Terms

a(0) =2a(1) =2a(2) =222a(3) =-1a(4) =-1a(5) =222a(6) =222222a(7) =-1a(8) =222222222a(9) =-1a(10) =22a(11) =-1a(12) =222222a(13) =222222a(14) =-1a(15) =-1a(17) =222222222a(19) =-1a(20) =222222a(21) =22a(23) =-1a(24) =-1a(25) =222222a(27) =-1a(29) =-1a(31) =-1a(32) =222222a(34) =-1a(35) =-1a(36) =222