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A115307 a(n) = if n<7 then n else 7*a(floor(n/7)) + 6 - n mod 7. 9


%S 1,2,3,4,5,6,13,12,11,10,9,8,7,20,19,18,17,16,15,14,27,26,25,24,23,22,

%T 21,34,33,32,31,30,29,28,41,40,39,38,37,36,35,48,47,46,45,44,43,42,97,

%U 96,95,94,93,92,91,90,89,88,87,86,85,84,83,82,81,80,79,78,77,76,75,74

%N a(n) = if n<7 then n else 7*a(floor(n/7)) + 6 - n mod 7.

%C Self-inverse permutation of the natural numbers;

%C A115310(n+5,6) = a(n);

%C if n is written in base 7 representation, then a(n) is the value after replacing all digits d (but not the leading one) by 6-d.

%H <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a>

%Y Cf. A054429, A115303, A115304, A115305, A115306, A115308, A115309, A106649.

%K nonn,base

%O 1,2

%A _Reinhard Zumkeller_, Jan 20 2006

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Last modified February 18 21:19 EST 2020. Contains 332028 sequences. (Running on oeis4.)