A361947 If the rightmost nonzero digit in the base-4 expansion of n is the digit 1, then replace 2's by 3's and vice versa; if it is the digit 2, then replace 1's by 3's and vice versa; if it is the digit 3, then replace 1's by 2's and vice versa; a(0) = 0.
0, 1, 2, 3, 4, 5, 14, 11, 8, 13, 10, 7, 12, 9, 6, 15, 16, 17, 50, 35, 20, 21, 62, 43, 56, 29, 58, 39, 44, 25, 54, 47, 32, 49, 34, 19, 52, 53, 46, 27, 40, 61, 42, 23, 28, 57, 38, 31, 48, 33, 18, 51, 36, 37, 30, 59, 24, 45, 26, 55, 60, 41, 22, 63, 64, 65, 194
Offset: 0
Examples
For n = 539: - the base-4 expansion of 539 is "20123", - the rightmost nonzero digit is 3, so we replace 1's by 2's and vice versa, - so the base-4 expansion of a(539) is "10213", and a(539) = 295.
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Programs
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PARI
a(n) = { my (m = if (n, [ [0,1,3,2], [0,3,2,1], [0,2,1,3] ][(n / 4^valuation(n, 4)) % 4], [0,1,2,3])); fromdigits(apply (d -> m[1+d], digits(n, 4)), 4); }
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