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

Author

Antti Karttunen, May 19 2008

Keywords

• nonn
• look
• hear

Links

• Antti Karttunen, Table of n, a(n) for n = 1..729
• Index entries for sequences that are permutations of the natural numbers

Crossrefs

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

Programs

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

Scheme

(string-append (define (A140266 n) (Z->N (A117966 (- n 1))))
(define (Z->N n) (if (positive? n) (* n 2) (+ 1 (* 2 (- n))))))

Formula

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