A115304 - OEIS

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

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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