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A085601
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a(n) = 2 * (4^n + 2^n) + 1.
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3
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5, 13, 41, 145, 545, 2113, 8321, 33025, 131585, 525313, 2099201, 8392705, 33562625, 134234113, 536903681, 2147549185, 8590065665, 34360000513, 137439477761, 549756862465, 2199025352705, 8796097216513, 35184380477441
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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COMMENTS
| 1. Begin with a square tile.
2. Place square tiles on each edge to form a diamond shape.
3. Count the tiles: a(0) = 5.
4. Add tiles to fill the enclosing square.
5. Go to step 2.
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FORMULA
| a(n)=7*a(n-1)-14*a(n-2)+8*a(n-3). G.f.: -(5-22*x+20*x^2)/((x-1)*(2*x-1)*(4*x-1)). [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 20 2009]
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CROSSREFS
| Cf. A028403, A046142, A056640, A064412.
Sequence in context: A046717 A080925 A164907 * A147718 A111009 A012172
Adjacent sequences: A085598 A085599 A085600 * A085602 A085603 A085604
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KEYWORD
| nonn,easy
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AUTHOR
| Jun Mizuki (suzuki32(AT)sanken.osaka-u.ac.jp), Jul 07 2003
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EXTENSIONS
| Edited by Franklin T. Adams-Watters (franktaw(AT)netscape.net) and Don Reble (djr(AT)nk.ca), Aug 15 2006
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