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A099427
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a(1) = 1; for n > 1, a(n) = 1 + greatest common divisor of n and a(n-1).
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3
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1, 2, 2, 3, 2, 3, 2, 3, 4, 3, 2, 3, 2, 3, 4, 5, 2, 3, 2, 3, 4, 3, 2, 3, 2, 3, 4, 5, 2, 3, 2, 3, 4, 3, 2, 3, 2, 3, 4, 5, 2, 3, 2, 3, 4, 3, 2, 3, 2, 3, 4, 5, 2, 3, 2, 3, 4, 3, 2, 3, 2, 3, 4, 5, 6, 7, 2, 3, 4, 3, 2, 3, 2, 3, 4, 5, 2, 3, 2, 3, 4, 3, 2, 3, 2, 3, 4, 5, 2, 3, 2, 3, 4, 3, 2, 3, 2, 3, 4, 5, 2, 3, 2, 3, 4
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OFFSET
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1,2
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COMMENTS
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LINKS
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EXAMPLE
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a(9)=4 because 1+gcd(a(8),9)=1+gcd(3,9)=1+3.
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MAPLE
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f:= proc(n) option remember; 1 + igcd(n, procname(n-1)) end proc:
f(1):= 1:
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MATHEMATICA
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a[1] = 1; a[n_] := a[n] = GCD[n, a[n - 1]] + 1; Table[ a[n], {n, 105}] (* Robert G. Wilson v, Nov 18 2004 *)
nxt[{n_, a_}]:={n+1, GCD[n+1, a]+1}; Transpose[NestList[nxt, {1, 1}, 110]] [[2]] (* Harvey P. Dale, Nov 22 2014 *)
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PROG
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(Haskell)
a099427 n = a099427_list !! (n-1)
a099427_list = 1 : map (+ 1) (zipWith gcd [2..] a099427_list)
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CROSSREFS
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For position of first occurrence of n see A060401.
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KEYWORD
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easy,nonn,nice
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AUTHOR
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Gaetan Polard (gaetan27(AT)hotmail.com), Nov 18 2004
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EXTENSIONS
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STATUS
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approved
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