A376295 The binary expansion of a(n) is the reversal of the concatenation of the binary expansions of 1,...,n.

1, 3, 27, 59, 1339, 7483, 122171, 253243, 19127611, 186899771, 7166221627, 32936025403, 1544764513595, 16937927302459, 544703508634939, 1107653462056251, 307352428123249979, 5495499198854061371, 466664101041592851771, 3418143152835121110331, 400096927713885319060795

Offset: 1

Author

Darío Clavijo, Sep 19 2024

Keywords

• nonn
• base
• easy

Examples

			For n = 4 a(4) = 59 because:
Concatenation:  1 10 11 100
Reversed order: 00111011
And 00111011 in base 10 is 59.
		

Links

• Paolo Xausa, Table of n, a(n) for n = 1..400

Crossrefs

Cf. A030101, A047778.

Programs

Mathematica

IntegerReverse[Module[{n = 1}, NestList[#*2^BitLength[++n] + n &, 1, 25]], 2] (* Paolo Xausa, Sep 30 2024 *)

Python

a = lambda n: int("".join(bin(x)[2:] for x in range(1,n+1))[::-1],2)
print([a(n) for n in range(1,22)])

Formula

a(n) = A030101(A047778(n)).