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A130449
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a(1) = 1; a(n) = 4^(n+1)*a(n-1)+1.
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0
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1, 17, 1089, 278785, 285475841, 1169309044737, 19157959388971009, 1255536026515604045825, 329131236134906506988748801, 345119115061395725472234262757377
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| The number of involutions in the group g_n D_{n+1} = G_n(operation) D_8.
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REFERENCES
| A. M. Cohen and D. E. Taylor, Title?, American Math Monthly, volume 114, Number 7, Aug-Sept 2007, pages 633-638
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FORMULA
| a(n)=2^(n^2)*8^n + Sum{k=1..n}{(1/2)^(k^2)*(1/8)^k}*2^(n^2)*8^n, n>=0 - Paolo P. Lava (paoloplava(AT)gmail.com), Jul 30 2008
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MATHEMATICA
| a[0] = 1; a[n_] := a[n] = 2^(2*n + 1)*2*a[n - 1] + 1 Table[a[n], {n, 0, 20}]
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CROSSREFS
| Sequence in context: A077645 A046731 A179157 * A130035 A032629 A075602
Adjacent sequences: A130446 A130447 A130448 * A130450 A130451 A130452
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KEYWORD
| nonn
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AUTHOR
| Roger L. Bagula (rlbagulatftn(AT)yahoo.com), Aug 07 2007
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EXTENSIONS
| Corrected definition and offset. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Dec 05 2008
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