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A347141
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a(1) = 11; for n > 1, a(n) is the smallest prime factor of 2^a(n-1) - 1.
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0
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OFFSET
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1,1
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LINKS
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EXAMPLE
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2^11 - 1 = 23*89, so the next term after 11 is 23.
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MATHEMATICA
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a[1] = 11; a[n_] := a[n] = Module[{p = 3}, While[PowerMod[2, a[n - 1], p] != 1, p = NextPrime[p]]; p]; Array[a, 5] (* Amiram Eldar, Aug 19 2021 *)
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CROSSREFS
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KEYWORD
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nonn,hard,more
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AUTHOR
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STATUS
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approved
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