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 A038449 #17 Mar 11 2025 09:44:35
%S A038449 1111111,10111111,11011111,11101111,11110111,11111011,11111101,
%T A038449 11111110,100111111,101011111,101101111,101110111,101111011,101111101,
%U A038449 101111110,110011111,110101111,110110111,110111011,110111101,110111110,111001111,111010111,111011011,111011101
%N A038449 Sums of 7 distinct powers of 10.
%H A038449 Amiram Eldar, <a href="/A038449/b038449.txt">Table of n, a(n) for n = 1..10000</a>
%t A038449 Take[Total/@Subsets[10^Range[0,20],{7}]//Union,20] (* _Harvey P. Dale_, Feb 25 2018 *)
%o A038449 (Python)
%o A038449 from itertools import islice
%o A038449 def A038449_gen(): # generator of terms
%o A038449 yield int(bin(n:=127)[2:])
%o A038449 while True: yield int(bin((n:=n^((a:=-n&n+1)|(a>>1)) if n&1 else ((n&~(b:=n+(a:=n&-n)))>>a.bit_length())^b))[2:])
%o A038449 A038449_list = list(islice(A038449_gen(),20)) # _Chai Wah Wu_, Mar 11 2025
%Y A038449 Cf. A011557.
%Y A038449 Cf. A038444, A038445, A038446, A038447, A038448, A038450, A038451, A038452, A038453, A038454.
%K A038449 nonn,easy
%O A038449 1,1
%A A038449 _Olivier Gérard_
%E A038449 Offset corrected by _Amiram Eldar_, Jul 12 2022