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| A163327
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Self-inverse permutation of integers: swap the odd- and even-positioned digits in the ternary expansion of n, then convert back to decimal.
(history;
published version)
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#21 by Michael De Vlieger at Fri Aug 05 15:35:09 EDT 2022
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#20 by Michel Marcus at Fri Aug 05 12:59:37 EDT 2022
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#19 by Michael S. Branicky at Fri Aug 05 12:55:21 EDT 2022
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#18 by Michael S. Branicky at Fri Aug 05 12:55:19 EDT 2022
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| PROG
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(Python)
from sympy.ntheory import digits
def a(n):
d = digits(n, 3)[1:]
return sum(3**(i+(1-2*(i&1)))*di for i, di in enumerate(d[::-1]))
print([a(n) for n in range(72)]) # Michael S. Branicky, Aug 05 2022
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| STATUS
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approved
editing
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#17 by Alois P. Heinz at Fri Jan 07 07:24:15 EST 2022
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#16 by Joerg Arndt at Fri Jan 07 02:33:57 EST 2022
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#15 by Michel Marcus at Fri Jan 07 01:25:22 EST 2022
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#14 by Michel Marcus at Fri Jan 07 01:25:18 EST 2022
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| LINKS
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A. Antti Karttunen, <a href="/A163327/b163327.txt">Table of n, a(n) for n = 0..728</a>
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| STATUS
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proposed
editing
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#13 by Jon E. Schoenfield at Fri Jan 07 00:15:22 EST 2022
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#12 by Jon E. Schoenfield at Fri Jan 07 00:15:21 EST 2022
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| NAME
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Self-inverse permutation of integers: swap the odd - and even-positioned digits in the ternary expansion of n, then convert back to decimal.
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| EXAMPLE
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11 in ternary base (A007089) is written as '(000...)102' (... + 0*27 + 1*9 + 0*3 + 2), which results '1020' = 1*27 + 0*9 + 2*3 + 0 = 33, when the odd - and even-positioned digits are swapped, thus a(11) = 33.
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| STATUS
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approved
editing
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