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A115305
a(n) = if n<5 then n else 5*a(floor(n/5)) + 4 - n mod 5.
10
1, 2, 3, 4, 9, 8, 7, 6, 5, 14, 13, 12, 11, 10, 19, 18, 17, 16, 15, 24, 23, 22, 21, 20, 49, 48, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33, 32, 31, 30, 29, 28, 27, 26, 25, 74, 73, 72, 71, 70, 69, 68, 67, 66, 65, 64, 63, 62, 61, 60, 59, 58, 57, 56, 55, 54, 53, 52
OFFSET
1,2
COMMENTS
Self-inverse permutation of the natural numbers;
A115310(n+3,4) = a(n);
if n is written in base 5 representation, then a(n) is the value after replacing all digits d (but not the leading one) by 4-d.
MATHEMATICA
Table[d = IntegerDigits[n, 5]; FromDigits[Prepend[4 - Rest@d, d[[1]]], 5], {n, 72}] (* Ivan Neretin, Apr 26 2017 *)
KEYWORD
nonn,base
AUTHOR
Reinhard Zumkeller, Jan 20 2006
STATUS
approved