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1, 3, 8, 21, 54, 137, 344, 857, 2122, 5229, 12836, 31413, 76686, 186833, 454448, 1103921, 2678674, 6494037, 15732284, 38089677, 92173782, 222961529, 539145416, 1303349513, 3150038746, 7611815613, 18390447188, 44426264421, 107310084894
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| Binomial transform of A052955.
Contribution from Johannes W. Meijer (meijgia(AT)hotmail.com), Aug 15 2010: (Start)
The sequence b(n)=2*a(n), n >= -1, is an elephant sequence, see A175654. For the corner squares 24 A[5] vectors, with decimal values between 23 and 464, lead to the b(n) sequence. For the central square these vectors lead to the companion sequence A175658.
(End)
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FORMULA
| G.f. : (1-x-x^2)/((1-2x)(1-2x-x^2)); a(n)=((1+sqrt(2))^n(3sqrt(2)/4+1)-(3sqrt(2)/4-1)(1-sqrt(2))^n)-2^n.
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CROSSREFS
| Cf. A000129.
Sequence in context: A038200 A030015 A103446 * A127358 A077849 A135473
Adjacent sequences: A094720 A094721 A094722 * A094724 A094725 A094726
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KEYWORD
| easy,nonn
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AUTHOR
| Paul Barry (pbarry(AT)wit.ie), May 23 2004
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