a(n) is the smallest composite number with the sum of digits = the n-th prime number.

Terms

a(0) =20a(1) =12a(2) =14a(3) =16a(4) =38a(5) =49a(6) =98a(7) =289a(8) =689a(9) =3899a(10) =5899a(11) =19999a(12) =68999a(13) =88999a(14) =299999a(15) =899999a(16) =5999999a(17) =7999999a(18) =49999999a(19) =98999999a(20) =199999999a(21) =889999999a(22) =2999999999a(23) =8999999999a(24) =88999999999a(25) =299999999999a(26) =499999999999a(27) =899999999999