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A111017 a(n) = (A102877(n+1) - A102877(n))/2. 1
0, 1, 2, 7, 20, 61, 180, 543, 1622, 4873, 14598, 43815, 131384, 394213, 1182456, 3547551, 10642110, 31926873, 95778990, 287338599, 862010924, 2586037645, 7758098316, 23274309567, 69822884886, 209468698473, 628405963974 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

First differences of A102877, divided by 2.

LINKS

Table of n, a(n) for n=0..26.

MATHEMATICA

a[0] := 1; a[1] := 1; a[n_] := If[EvenQ[n], 3*a[n - 1], 3*a[n - 1] - 2*a[(n - 3)/2]]; Table[(a[i + 1] - a[i])/2, {i, 1, 50}] (* Stefan Steinerberger, May 22 2007 *)

PROG

(PARI) {m=27; v=vector(m+1); v[1]=1; v[2]=1; for(n=2, m, k=3*v[n]; if(n%2==1, k=k-2*v[(n-1)/2]); v[n+1]=k); w=vector(m, n, (v[n+1]-v[n])/2); print(w)} /* Klaus Brockhaus, May 20 2007 */

CROSSREFS

Cf. A102877.

Sequence in context: A025180 A201967 A116950 * A116408 A015518 A014983

Adjacent sequences:  A111014 A111015 A111016 * A111018 A111019 A111020

KEYWORD

nonn

AUTHOR

Paul Curtz, May 17 2007

EXTENSIONS

Edited and extended by Klaus Brockhaus and Stefan Steinerberger, May 20 2007

STATUS

approved

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Last modified October 16 05:52 EDT 2019. Contains 328045 sequences. (Running on oeis4.)