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 A300571 #18 Feb 26 2023 10:58:08 %S A300571 0,10,1010,111010,100111010,101100111010,110101100111010, %T A300571 111110101100111010,1000111110101100111010,10011000111110101100111010, %U A300571 101010011000111110101100111010,1011101010011000111110101100111010,11001011101010011000111110101100111010 %N A300571 a(n) is the concatenation n in base 2, n-1 in base 2, ..., 0 in base 2. %H A300571 Seiichi Manyama, <a href="/A300571/b300571.txt">Table of n, a(n) for n = 0..155</a> %F A300571 a(n) = A300570(n)*10. - _Chai Wah Wu_, Feb 26 2023 %o A300571 (Python) %o A300571 from functools import reduce %o A300571 def A300571(n): return int(bin(reduce(lambda i,j:(i<<j.bit_length())+j,range(n,0,-1),0))[2:])*10 # _Chai Wah Wu_, Feb 26 2023 %Y A300571 Cf. A007088, A058935, A300570. %K A300571 nonn,base %O A300571 0,2 %A A300571 _Seiichi Manyama_, Mar 08 2018