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A006695
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a(2n)=2*a(2n-2)^2-1, a(2n+1)=2*a(2n)-1, a(0)=2.
(Formerly M0838)
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2
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2, 3, 7, 13, 97, 193, 18817, 37633, 708158977, 1416317953, 1002978273411373057, 2005956546822746113, 2011930833870518011412817828051050497, 4023861667741036022825635656102100993
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OFFSET
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0,1
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COMMENTS
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An infinite coprime sequence defined by recursion.
Every term is relatively prime to all others. - Michael Somos, Feb 01 2004
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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FORMULA
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MATHEMATICA
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nxt[{n_, a_, b_}]:=If[OddQ[n], {n+1, b, 2a^2-1}, {n+1, b, 2b-1}]; Transpose[ NestList[ nxt, {1, 2, 3}, 15]][[2]] (* Harvey P. Dale, Jun 22 2015 *)
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PROG
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(PARI) a(n)=if(n<1, 2*(n==0), if(n%2, 2*a(n-1)-1, 2*a(n-2)^2-1))
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CROSSREFS
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KEYWORD
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nonn,easy,nice
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AUTHOR
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STATUS
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approved
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