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 A201021 #9 Mar 29 2023 11:59:51
%S A201021 117,171,711,1711,7111,11711,17111,71111,111117,111171,111711,117111,
%T A201021 171111,711111,1111117,1111171,1711111,7111111,11111711,11117111,
%U A201021 11171111,11711111,17111111,111111117,111111171,111111711,111117111,111171111,111711111,117111111,171111111
%N A201021 Composite numbers whose multiplicative digital root is 7.
%C A201021 Also composite numbers whose product of digits is 7.
%C A201021 Complement of A107693 with respect to A034054. ~
%F A201021 Number 171 is in sequence because 1*7*1=7.
%t A201021 Flatten[Table[Select[FromDigits/@Permutations[PadRight[{7},n,1]],CompositeQ],{n,9}]]//Sort (* _Harvey P. Dale_, Mar 29 2023 *)
%Y A201021 Cf. A107693 (primes whose multiplicative digital root is 7), A034054 (numbers whose multiplicative digital root is 7).
%K A201021 nonn,base
%O A201021 1,1
%A A201021 _Jaroslav Krizek_, Nov 25 2011