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A103889 Odd and even positive integers swapped. 17
2, 1, 4, 3, 6, 5, 8, 7, 10, 9, 12, 11, 14, 13, 16, 15, 18, 17, 20, 19, 22, 21, 24, 23, 26, 25, 28, 27, 30, 29, 32, 31, 34, 33, 36, 35, 38, 37, 40, 39, 42, 41, 44, 43, 46, 45, 48, 47, 50, 49, 52, 51, 54, 53, 56, 55, 58, 57, 60, 59, 62, 61, 64, 63, 66, 65, 68, 67, 70, 69, 72, 71 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

(a(n)-1)*(a(n-1)+1) = 2*A176222(n+1) for n>1; (a(n)-1)*(a(n-3)+1) = 2*A176222(n) for n>3. [Bruno Berselli, Nov 16 2010]

LINKS

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

Index entries for linear recurrences with constant coefficients, signature (1,1,-1).

FORMULA

a(2k) = 2k-1 = A005408(k), a(2k-1) = 2k = A005843(k), k=1, 2, ...

O.g.f.: x*(x^2-x+2)/[(x-1)^2*(1+x)]. - R. J. Mathar, Apr 06 2008

a(n) = n-1+2*(n mod 2). - Rolf Pleisch, Apr 22 2008

a(n) = 2*n-a(n-1)-1 (with a(1)=2). [Vincenzo Librandi, Nov 16 2010]

a(n) = n-(-1)^n. a(n)-a(n-1)-a(n-2)+a(n-3) = 0 for n>3. [Bruno Berselli, Nov 16 2010]

MATHEMATICA

Table[{n + 1, n}, {n, 1, 100, 2}] // Flatten

PROG

[ n eq 1 select 2 else -Self(n-1)+2*n-1: n in [1..72] ];

(Haskell)

import Data.List (transpose)

a103889 n = n - 1 + 2 * mod n 2

a103889_list = concat $ transpose [tail a005843_list, a005408_list]

-- Reinhard Zumkeller, Jun 23 2013, Feb 21 2011

(PARI) a(n)=n-1+if(n%2, 2) \\ Charles R Greathouse IV, Feb 24 2011

CROSSREFS

Essentially the same as A014681.

Odd numbers: A005408. Even numbers: A005843.

Cf. A103889, A004442.

Sequence in context: A167419 A114285 A014681 * A137805 A163501 A096779

Adjacent sequences:  A103886 A103887 A103888 * A103890 A103891 A103892

KEYWORD

nonn,easy

AUTHOR

Zak Seidov, Feb 20 2005

STATUS

approved

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Last modified May 24 11:18 EDT 2017. Contains 286975 sequences.