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A138173
a(n) is the smallest m such that m^3 begins with n^2.
3
1, 16, 21, 55, 63, 154, 17, 4, 201, 10, 23, 113, 257, 27, 609, 295, 307, 148, 1535, 342, 164, 1692, 809, 1793, 397, 878, 9, 428, 944, 4482, 987, 1008, 1029, 4872, 107, 2349, 5154, 5247, 2478, 252, 552, 5609, 5697, 5785, 2726, 1284, 2806, 6131, 2885
OFFSET
1,2
COMMENTS
Differs from A030691.
FORMULA
a(n) = (A138174(n))^(1/3).
PROG
(Sage)
A138173 = lambda n: next(m for m in IntegerRange(1, infinity) if str(m**3).startswith(str(n**2)))
# D. S. McNeil, Dec 12 2010
(Python)
from gmpy2 import iroot
def A138173(n):
d, nd = 1, n**2
while True:
x = iroot(nd-1, 3)[0]+1
if x**3 < nd+d:
return int(x)
d *= 10
nd *= 10 # Chai Wah Wu, May 24 2016
KEYWORD
nonn,base
AUTHOR
Zak Seidov, Mar 05 2008
STATUS
approved