This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A280390 #6 Jan 03 2017 03:04:02
%S A280390 25,125,127,128,216,289,343,347,625,736,1285,1296,1792,2048,2187
%N A280390 Integers that can be written using their individual decimal digits and the operations + - * / ^ but not the concatenation of their digits.
%C A280390 A proper subset of A036057.
%e A280390 125 is in the sequence since 5^(1+2) but 121 is not in the sequence. We do not accept 11^2 since 11 is the concatenation of two digits.
%t A280390 ops = {Plus, Subtract, Times, Divide, Power}; fQ[n_] := Length@ Select[ Groupings[ Permutations@ IntegerDigits@ n, ops -> 2], # == n &] > 0; k = 1; lst = {}; While[k < 1001, If[fQ@k, AppendTo[lst, k]]; k++]; lst (* requires Mathematica version 11 or better *)
%Y A280390 Cf. A036057.
%K A280390 base,nonn
%O A280390 1,1
%A A280390 _Erich Friedman_ and _Robert G. Wilson v_, Jan 01 2017