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A321464
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Reverse nonzero digits in ternary expansion of n and convert back to decimal.
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7
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0, 1, 2, 3, 4, 7, 6, 5, 8, 9, 10, 19, 12, 13, 22, 21, 16, 25, 18, 11, 20, 15, 14, 23, 24, 17, 26, 27, 28, 55, 30, 31, 58, 57, 34, 61, 36, 37, 64, 39, 40, 67, 66, 49, 76, 63, 46, 73, 48, 43, 70, 75, 52, 79, 54, 29, 56, 33, 32, 59, 60, 35, 62, 45, 38, 65, 42, 41
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OFFSET
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0,3
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COMMENTS
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This sequence is a self-inverse permutation of nonnegative integers with fixed points A321473.
See A321474 for the decimal variant.
The binary variant simply corresponds to the identity (A001477).
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LINKS
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FORMULA
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a(3 * n) = 3 * a(n).
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EXAMPLE
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The first values at prime indices, alongside the corresponding ternary expansions, are:
n a(n) ter(n) ter(a(n))
-- ---- ------ ---------
2 2 2 2
3 3 10 10
5 7 12 21
7 5 21 12
11 19 102 201
13 13 111 111
17 25 122 221
19 11 201 102
23 23 212 212
29 55 1002 2001
31 31 1011 1011
37 37 1101 1101
41 67 1112 2111
43 49 1121 1211
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MATHEMATICA
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a[n_] := Block[{x = IntegerDigits[n, 3], t}, t = Flatten@ Position[x, 1 | 2]; x[[Reverse@ t]] = x[[t]]; FromDigits[x, 3]]; Array[a, 68, 0] (* Giovanni Resta, Sep 17 2019 *)
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PROG
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(PARI) a(n, base=3) = my (d=digits(n, base), t=Vecrev(select(sign, d)), i=0); for (j=1, #d, if (d[j], d[j] = t[i++])); fromdigits(d, base)
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CROSSREFS
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KEYWORD
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AUTHOR
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STATUS
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approved
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