A348354 The base-5 expansion of a(n) is obtained by replacing 1's, 2's, 3's and 4's by 3's, 4's, 1's and 2's, respectively, in the base-5 expansion of n.
0, 3, 4, 1, 2, 15, 18, 19, 16, 17, 20, 23, 24, 21, 22, 5, 8, 9, 6, 7, 10, 13, 14, 11, 12, 75, 78, 79, 76, 77, 90, 93, 94, 91, 92, 95, 98, 99, 96, 97, 80, 83, 84, 81, 82, 85, 88, 89, 86, 87, 100, 103, 104, 101, 102, 115, 118, 119, 116, 117, 120, 123, 124, 121
Offset: 0
Examples
The first terms, in decimal and in base 5, are: n a(n) q(n) q(a(n)) -- ---- ---- ------- 0 0 0 0 1 3 1 3 2 4 2 4 3 1 3 1 4 2 4 2 5 15 10 30 6 18 11 33 7 19 12 34 8 16 13 31 9 17 14 32 10 20 20 40
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Programs
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Mathematica
a[n_] := With[{d = {0, 3, 4, 1, 2}}, FromDigits[d[[IntegerDigits[n, 5] + 1]], 5]]; Array[a, 64, 0] (* Amiram Eldar, Oct 16 2021 *) -
PARI
a(n, p=[3,4,1,2]) = fromdigits(apply(d -> if (d, p[d], 0), digits(n, #p+1)), #p+1)
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