A140266 Inverse permutation to A140265.

1, 2, 3, 6, 8, 4, 7, 5, 9, 18, 20, 16, 24, 26, 22, 12, 14, 10, 19, 17, 21, 13, 11, 15, 25, 23, 27, 54, 56, 52, 60, 62, 58, 48, 50, 46, 72, 74, 70, 78, 80, 76, 66, 68, 64, 36, 38, 34, 42, 44, 40, 30, 32, 28, 55, 53, 57, 49, 47, 51, 61, 59, 63, 37, 35, 39, 31, 29, 33, 43, 41, 45

Offset

1,2

Links

A. Karttunen, Table of n, a(n) for n = 1..729

Index entries for sequences that are permutations of the natural numbers

Formula

a(n) = Z->N(A117966(n-1)), where Z->N(z) = 2z if z>0 else 2|z|+1.

Prog

(Scheme:) (string-append (define (A140266 n) (Z->N (A117966 (- n 1))))
(define (Z->N n) (if (positive? n) (* n 2) (+ 1 (* 2 (- n))))))
(Python)
def a117966(n):
    if n==0: return 0
    if n%3==0: return 3*a117966(n/3)
    elif n%3==1: return 3*a117966((n - 1)/3) + 1
    else: return 3*a117966((n - 2)/3) - 1
def Z(z): return 2*z if z>0 else 2*abs(z) + 1
def a(n): return Z(a117966(n - 1)) # Indranil Ghosh, Jun 07 2017

Crossrefs

Inverse: A140265. a(n) = A140264(n-1)+1.

Sequence in context: A133441 A086254 A265297 * A140265 A349917 A191453

Adjacent sequences: A140263 A140264 A140265 * A140267 A140268 A140269

Keyword

nonn,look,hear

Author

Antti Karttunen, May 19 2008

Status

approved