OFFSET
0,3
FORMULA
a(2^k) = 2^(k+1)-1.
a(2^k-1) = (8*2^k-8-5*k-k^2)/2. - Giovanni Resta, Dec 02 2019
EXAMPLE
For n = 5: 5 in binary is 101, so a(n) = 101 + 10 + 01 + 1 + 0 + 1 in binary, which is 5 + 2 + 1 + 1 + 0 + 1 = 10.
MATHEMATICA
a[n_] := Block[{d = IntegerDigits[n, 2]}, Sum[FromDigits[Take[d, {i, j}], 2], {j, Length[d]}, {i, j}]]; Array[a, 61, 0] (* Giovanni Resta, Dec 02 2019 *)
PROG
(Python)
def bitlist(n):
output = []
while n != 0:
output.append(n % 2)
n /= 2
return output
#converts a number into a list of the digits in binary reversed
def bitsum(bitlist):
output = 0
for bit in bitlist:
if bit == 1:
output += 1
return output
#gives the cross sum of a bitlist
def a(bitlist):
output = 0
l = len(bitlist)
for x in range(l):
output += bitlist[x] * (l - x) * (2**(x + 1) - 1)
return output
#to get the first n numbers of the sequence, write:
for x in range(1, n + 1):
print x, a(bitlist(x))
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Tonio Kettner, Nov 30 2019
STATUS
approved