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 A376295 #33 Sep 30 2024 12:53:29
%S A376295 1,3,27,59,1339,7483,122171,253243,19127611,186899771,7166221627,
%T A376295 32936025403,1544764513595,16937927302459,544703508634939,
%U A376295 1107653462056251,307352428123249979,5495499198854061371,466664101041592851771,3418143152835121110331,400096927713885319060795
%N A376295 The binary expansion of a(n) is the reversal of the concatenation of the binary expansions of 1,...,n.
%H A376295 Paolo Xausa, <a href="/A376295/b376295.txt">Table of n, a(n) for n = 1..400</a>
%F A376295 a(n) = A030101(A047778(n)).
%e A376295 For n = 4 a(4) = 59 because:
%e A376295 Concatenation: 1 10 11 100
%e A376295 Reversed order: 00111011
%e A376295 And 00111011 in base 10 is 59.
%t A376295 IntegerReverse[Module[{n = 1}, NestList[#*2^BitLength[++n] + n &, 1, 25]], 2] (* _Paolo Xausa_, Sep 30 2024 *)
%o A376295 (Python)
%o A376295 a = lambda n: int("".join(bin(x)[2:] for x in range(1,n+1))[::-1],2)
%o A376295 print([a(n) for n in range(1,22)])
%Y A376295 Cf. A030101, A047778.
%K A376295 nonn,base,easy
%O A376295 1,2
%A A376295 _Darío Clavijo_, Sep 19 2024