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A058935
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Concatenation of first n binary numbers.
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12
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0, 1, 110, 11011, 11011100, 11011100101, 11011100101110, 11011100101110111, 110111001011101111000, 1101110010111011110001001, 11011100101110111100010011010, 110111001011101111000100110101011, 1101110010111011110001001101010111100
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OFFSET
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0,3
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COMMENTS
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If the terms are read as decimal numbers, which of them are primes? For example, a(5) = 11011100101 = 1193*9229757 is not a prime. - N. J. A. Sloane, Feb 17 2023
Answer: a(231) is the first prime term when read as a decimal number; a(15) is the first when read as a binary number. - Michael S. Branicky, Feb 17 2023
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LINKS
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FORMULA
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MATHEMATICA
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FromDigits /@ Flatten /@ Rest[FoldList[Append, {}, IntegerDigits[Range[10], 2]]] (* Eric W. Weisstein, Nov 04 2015 *)
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PROG
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(Python)
from itertools import count, islice
def agen(s=""): yield from (int(s:=s+bin(n)[2:]) for n in count(0))
(Python)
from functools import reduce
def A058935(n): return int(bin(reduce(lambda i, j:(i<<j.bit_length())+j, range(n+1)))[2:]) # Chai Wah Wu, Feb 26 2023
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CROSSREFS
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Cf. A047778 for this converted to decimal, A001855 (offset) for number of digits.
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KEYWORD
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base,easy,nonn
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AUTHOR
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STATUS
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approved
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