A115303 a(n) = n if n < 3, otherwise 3*a(floor(n/3)) + 2 - n mod 3.

1, 2, 5, 4, 3, 8, 7, 6, 17, 16, 15, 14, 13, 12, 11, 10, 9, 26, 25, 24, 23, 22, 21, 20, 19, 18, 53, 52, 51, 50, 49, 48, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33, 32, 31, 30, 29, 28, 27, 80, 79, 78, 77, 76, 75, 74, 73, 72, 71, 70, 69, 68, 67, 66, 65, 64, 63, 62

Offset

1,2

Comments

Self-inverse permutation of the natural numbers;

A115310(n+1,2) = a(n);

if n is written in ternary representation, then a(n) is the value after replacing all digits d (but not the leading one) with 2-d.

a(n+1) = a(n)-1 unless n = 3^k - 1 or 2*3^k-1 for some k. - Robert Israel, Feb 28 2023

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Index entries for sequences that are permutations of the natural numbers

Maple

a:= proc(n) option remember;
   3*procname(floor(n/3))+2 - (n mod 3)
end proc:
a(1):= 1: a(2):= 2:
map(a, [$1..100]); # Robert Israel, Feb 28 2023

Crossrefs

Cf. A054429, A115304, A115305, A115306, A115307, A115308, A115309, A106649.

Sequence in context: A361945 A171837 A216253 * A266403 A266415 A132664

Adjacent sequences: A115300 A115301 A115302 * A115304 A115305 A115306

Keyword

nonn,base,look

Author

Reinhard Zumkeller, Jan 20 2006

Status

approved