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A097140 Interleave n and 1-n. 3
0, 1, 1, 0, 2, -1, 3, -2, 4, -3, 5, -4, 6, -5, 7, -6, 8, -7, 9, -8, 10, -9, 11, -10, 12, -11, 13, -12, 14, -13, 15, -14, 16, -15, 17, -16, 18, -17, 19, -18, 20, -19, 21, -20, 22, -21, 23, -22, 24, -23, 25, -24, 26, -25, 27, -26, 28, -27, 29, -28, 30, -29, 31, -30, 32, -31 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,5

COMMENTS

Partial sums are A097141. Binomial transform is x(1+x)/(1-2x), or A003945 with a leading 0.

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 0..1000

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

FORMULA

G.f. : x(1+2x)/((1-x)(1+x)^2); a(n)=3/4+(2n-3)(-1)^n/4.

a(0)=0, a(1)=1, a(2)=1, a(n)=a(n-1)+a(n-2)+a(n-3) [From Harvey P. Dale, Mar 26 2012]

G.f.: x*G(0)/(1+x) where G(k) = 1 + 2*x/(1 - x/(x + 2/G(k+1) )); (recursively defined continued fraction). - Sergei N. Gladkovskii, Dec 21 2012

MATHEMATICA

With[{nn=35}, Riffle[Range[0, nn], Range[1, -(nn-1), -1]]] (* or *) LinearRecurrence[ {-1, 1, 1}, {0, 1, 1}, 70] (* Harvey P. Dale, Mar 26 2012 *)

PROG

(Haskell)

import Data.List (transpose)

a097140 n = a097140_list !! n

a097140_list = concat $ transpose [a001477_list, map (1 -) a001477_list]

-- Reinhard Zumkeller, Nov 27 2012

(PARI) a(n)=3/4+(2*n-3)*(-1)^n/4 \\ Charles R Greathouse IV, Sep 02 2015

CROSSREFS

Cf. A001477.

Sequence in context: A213633 A289436 A282745 * A028242 A030451 A241825

Adjacent sequences:  A097137 A097138 A097139 * A097141 A097142 A097143

KEYWORD

easy,sign

AUTHOR

Paul Barry, Jul 29 2004

STATUS

approved

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Last modified July 17 16:58 EDT 2019. Contains 325107 sequences. (Running on oeis4.)