login
A376295
The binary expansion of a(n) is the reversal of the concatenation of the binary expansions of 1,...,n.
1
1, 3, 27, 59, 1339, 7483, 122171, 253243, 19127611, 186899771, 7166221627, 32936025403, 1544764513595, 16937927302459, 544703508634939, 1107653462056251, 307352428123249979, 5495499198854061371, 466664101041592851771, 3418143152835121110331, 400096927713885319060795
OFFSET
1,2
LINKS
FORMULA
a(n) = A030101(A047778(n)).
EXAMPLE
For n = 4 a(4) = 59 because:
Concatenation: 1 10 11 100
Reversed order: 00111011
And 00111011 in base 10 is 59.
MATHEMATICA
IntegerReverse[Module[{n = 1}, NestList[#*2^BitLength[++n] + n &, 1, 25]], 2] (* Paolo Xausa, Sep 30 2024 *)
PROG
(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)])
CROSSREFS
Sequence in context: A201276 A053360 A176963 * A204046 A305094 A120117
KEYWORD
nonn,base,easy
AUTHOR
Darío Clavijo, Sep 19 2024
STATUS
approved