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