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 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 (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)=9, because 9^2 = 81 = 1010001_2 begins with 1010 = 10_2. PROG (Python) from gmpy2 import isqrt def A272679(n): if n == 0: return 0 else: d, nd = 1, n while True: x = isqrt(nd-1)+1 if x**2 < nd+d: return int(x) d *= 2 nd *= 2 # Chai Wah Wu, May 22 2016 CROSSREFS Cf. A007088, A018851, A018796, A272680, A272681. Sequence in context: A347378 A336853 A273580 * A119764 A178310 A210697 Adjacent sequences: A272676 A272677 A272678 * A272680 A272681 A272682 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 September 11 15:52 EDT 2024. Contains 375836 sequences. (Running on oeis4.)