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A084186 First occurrence of exactly n 1's in the binary expansion of sqrt(2). 5
1, 3, 40, 17, 74, 265, 31, 336, 11937, 1403, 8894, 3524, 33223, 126903, 3067, 109312, 390536, 553171, 280266, 962560, 1747112, 1740081, 30793169, 13109551, 118101037, 1077718187, 44908294, 1528865059, 1647265647, 3913429742, 10501492774, 4702573600, 81557258556, 107498528405 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
Nick Hobson, C program
EXAMPLE
The binary expansion of sqrt(2) is 1.0110101000001..(A004539) and at position 17, there are four 1's, framed by 0's, so a(4)=17.
PROG
(Python)
from itertools import count
from math import isqrt
def A084186(n):
a, b = 2, (1<<n+2)-1
c = (b>>1)^1
for k in count(1-n):
if isqrt(a)&b==c:
return k
a<<=2 # Chai Wah Wu, Jan 24 2024
(C) See Links section.
CROSSREFS
Cf. A233836.
Sequence in context: A319955 A317484 A196159 * A037104 A100306 A101014
KEYWORD
base,nonn,hard
AUTHOR
Ralf Stephan, May 18 2003
EXTENSIONS
a(21)-a(29) from Chai Wah Wu, Jan 25 2024
a(30)-a(34) from Nick Hobson, Feb 15 2024
STATUS
approved

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Last modified July 23 13:44 EDT 2024. Contains 374549 sequences. (Running on oeis4.)