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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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 REFERENCES Allan C. Wechsler, posting to math-fun mailing list May 22 2016. LINKS Chai Wah Wu, Table of n, a(n) for n = 0..10000 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 Cf. A007088, A018851, A018796, A272679, A272681. Sequence in context: A162187 A103644 A185070 * A082202 A283452 A051514 Adjacent sequences:  A272677 A272678 A272679 * A272681 A272682 A272683 KEYWORD nonn,base,easy AUTHOR N. J. A. Sloane, May 22 2016 EXTENSIONS More terms from Chai Wah Wu, May 22 2016 STATUS approved

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Last modified May 31 00:53 EDT 2020. Contains 334747 sequences. (Running on oeis4.)