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9, 9, 9, 9, 15, 15, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 27, 27, 33, 33, 33, 33, 33, 45, 45, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 57, 57, 57, 57, 57, 57, 57, 69, 69, 75, 75, 75, 75, 75, 75, 77, 77, 77, 77, 77, 77, 77, 77, 77, 77, 77, 77, 77, 105, 105, 105
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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LINKS
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MATHEMATICA
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terms = 70; max = 2 terms;
f[lst_] := Block[{k = 4}, While[GCD[lst[[-2]], k] == 1 || GCD[lst[[-1]], k] > 1 || MemberQ[lst, k], k++]; Append[lst, k]];
A098550 = Nest[f, {1, 2, 3}, max-3];
sel = Select[Transpose[{Range[max], A098550}], PrimeQ[#[[2]]]&][[All, 1]]+2;
a[n_] := For[k = 1, k <= max, k = k+2, If[CompositeQ[k] && FreeQ[A098550[[1 ;; n]], k] && FreeQ[A251542, k], Return[k]]];
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PROG
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(Haskell)
import Data.List (delete); import Data.List.Ordered (minus)
a251558 n = a251558_list !! (n-1)
a251558_list = 9 : 9 : 9 : f 2 3 [4..] (tail a014076_list) where
f u v ws zs = g ws where
g (x:xs) = if gcd x u > 1 && gcd x v == 1
then y : f v x (delete x ws) ys else g xs
where ys@(y:_) = zs `minus` [x]
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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