A064664 - OEIS

A064664

Regard A064413 as giving a permutation of the positive integers; sequence gives inverse permutation.

1, 2, 5, 3, 10, 4, 14, 8, 6, 9, 20, 7, 28, 13, 11, 17, 33, 12, 37, 18, 15, 19, 43, 16, 24, 27, 22, 26, 57, 23, 61, 31, 21, 32, 25, 30, 67, 36, 29, 40, 74, 35, 81, 41, 39, 42, 89, 45, 50, 46, 34, 47, 100, 48, 53, 49, 38, 56, 107, 52, 115, 60, 51, 64, 54, 59, 128, 65, 44, 55

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OFFSET

1,2

COMMENTS

The Mathematica program computes the EKG sequence A064413 and then determines the inverse permutation. - T. D. Noe, Nov 13 2002

LINKS

Ray Chandler, Table of n, a(n) for n = 1..10000 (first 1000 terms from T. D. Noe)

J. C. Lagarias, E. M. Rains, and N. J. A. Sloane, The EKG sequence, Exper. Math. 11 (2002), 437-446; arXiv preprint, arXiv:math/0204011 [math.NT], 2002.

Eric Weisstein's World of Mathematics, EKG Sequence.

Index entries for sequences related to EKG sequence.

Index entries for sequences that are permutations of the natural numbers

EXAMPLE

Original permutation has cycles (1) (2) (3, 4, 6, 9, 10, 5) (..., 20, 18, 12, 7, 14, 13, 28, 26, ...) (8) ...

MATHEMATICA

maxN=200; lst={1, 2}; unused=Range[3, maxN]; found=True; While[found, found=False; i=0; While[ !found&&i<Length[unused], i++; If[GCD[lst[[ -1]], unused[[i]]]>1, found=True; AppendTo[lst, unused[[i]]]; unused=Delete[unused, i]]]]; Take[Ordering[lst], unused[[1]]-1]

PROG

(Haskell)

import Data.List (elemIndex); import Data.Maybe (fromJust)

a064664 = (+ 1) . fromJust . (`elemIndex` a064413_list)

-- Reinhard Zumkeller, May 01 2014, Sep 17 2011

CROSSREFS

Cf. A064413, A064665, A064666, A064667, A064668, A064669.

Equals A064421 + 1.

Sequence in context: A163233 A096666 A191855 * A352188 A323637 A349637

Adjacent sequences: A064661 A064662 A064663 * A064665 A064666 A064667

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Oct 11 2001

STATUS

approved