A115304 a(n) = n if n < 4, otherwise 4*a(floor(n/4)) + 3 - n mod 4.

1, 2, 3, 7, 6, 5, 4, 11, 10, 9, 8, 15, 14, 13, 12, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33, 32, 63, 62, 61, 60, 59, 58, 57, 56, 55, 54, 53, 52, 51, 50, 49, 48, 127, 126, 125, 124, 123, 122, 121

Offset

1,2

Comments

Self-inverse permutation of the natural numbers.

If n is written in base-4 representation, then a(n) is the value after replacing all digits d (except for the leading one) by 3-d.

Links

Paolo Xausa, Table of n, a(n) for n = 1..10000

Index entries for sequences that are permutations of the natural numbers

Formula

a(n) = A115310(n+2,3).

Mathematica

A115304[n_] := FromDigits[MapAt[3 - # &, IntegerDigits[n, 4], 2;; ], 4];
Array[A115304, 100] (* Paolo Xausa, May 20 2024 *)

Crossrefs

Cf. A054429, A115303, A115305, A115306, A115307, A115308, A115309, A106649.

Sequence in context: A069772 A277819 A098287 * A277901 A277902 A098285

Adjacent sequences: A115301 A115302 A115303 * A115305 A115306 A115307

Keyword

nonn,base

Author

Reinhard Zumkeller, Jan 20 2006

Status

approved