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A272680
Smallest square that begins with n (in binary).
3
0, 1, 4, 25, 4, 81, 25, 121, 16, 9, 81, 361, 25, 441, 225, 121, 16, 1089, 36, 625, 81, 169, 361, 1521, 49, 25, 841, 441, 225, 3721, 121, 2025, 64, 529, 1089, 4489, 36, 2401, 1225, 625, 81, 5329, 169, 2809, 11449, 361, 5929, 1521, 6241, 49, 100, 6561, 841, 6889
OFFSET
0,3
REFERENCES
Allan C. Wechsler, posting to math-fun mailing list May 22 2016.
EXAMPLE
a(10)=81, because 81 = 9^2 = 1010001_2 begins with 1010 = 10_2.
PROG
(Python)
from gmpy2 import isqrt
def A272680(n):
if n == 0:
return 0
else:
d, nd = 1, n
while True:
x = (isqrt(nd-1)+1)**2
if x < nd+d:
return int(x)
d *= 2
nd *= 2 # Chai Wah Wu, May 22 2016
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
N. J. A. Sloane, May 22 2016
EXTENSIONS
More terms from Chai Wah Wu, May 22 2016
STATUS
approved