

A272679


a(n)^2 is the smallest square whose binary expansion begins with the binary expansion of n.


5



0, 1, 2, 5, 2, 9, 5, 11, 4, 3, 9, 19, 5, 21, 15, 11, 4, 33, 6, 25, 9, 13, 19, 39, 7, 5, 29, 21, 15, 61, 11, 45, 8, 23, 33, 67, 6, 49, 35, 25, 9, 73, 13, 53, 107, 19, 77, 39, 79, 7, 10, 81, 29, 83, 59, 21, 15, 43, 61, 87, 11, 89, 63, 45, 8, 129, 23, 93, 33, 47
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OFFSET

0,3


REFERENCES

Allan C. Wechsler, posting to mathfun mailing list May 22 2016.


LINKS



EXAMPLE

a(10)=9, because 9^2 = 81 = 1010001_2 begins with 1010 = 10_2.


PROG

(Python)
from gmpy2 import isqrt
if n == 0:
return 0
else:
d, nd = 1, n
while True:
x = isqrt(nd1)+1
if x**2 < nd+d:
return int(x)
d *= 2


CROSSREFS



KEYWORD

nonn,base,easy


AUTHOR



EXTENSIONS



STATUS

approved



