A138607 List first A008578(1) odd numbers, then first A008578(2) even numbers, then the next A008578(3) odd numbers, then the next A008578(4) even numbers, etc.

1, 2, 4, 3, 5, 7, 6, 8, 10, 12, 14, 9, 11, 13, 15, 17, 19, 21, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 49, 51, 53, 55, 57, 59, 61, 63, 65, 67, 69, 71, 73

Offset

1,2

Comments

A permutation of numbers.

Links

Table of n, a(n) for n=1..72.

Index entries for sequences that are permutations of the natural numbers

Formula

If n < 3, a(n) = n. If n-2 = A007504(A083375(n-2)), then a(n) = a(n-1-A000040(A083375(n-2)))+2, otherwise a(n) = a(n-1)+2. - Antti Karttunen, Oct 05 2009.

Example

Let
  S1={1}
  S2={2,4}
  S3={3,5,7}
  S4={6,8,10,12,14}
  S5={9,11,13,15,17,19,21}
  S6={16,18,20,22,24,26,28,30,32,34,36}
  ...
then S1, S2, S3, S4, S5, S6,... gives this sequence.

Prog

(MIT Scheme:) (define (A138607 n) (if (< n 3) n (let ((k (A083375 (- n 2)))) (if (= (- n 2) (A007504 k)) (+ 2 (A138607 (- n 1 (A000040 k)))) (+ 2 (A138607 (-1+ n))))))) ;; Antti Karttunen, Oct 05 2009

Crossrefs

Inverse: A166014. Cf. A138606, A138608, A138609, A138612.

Sequence in context: A236348 A143097 A074147 * A372341 A166014 A357527

Adjacent sequences: A138604 A138605 A138606 * A138608 A138609 A138610

Keyword

nonn,tabf

Author

Ctibor O. Zizka, May 14 2008

Extensions

Edited, extended, and offset changed from 0 to 1 by Antti Karttunen, Oct 05 2009

Status

approved