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 A130172 Let f(i) = prime( f(i - 1) (modulo 10^n) ) with f(0) = 1; a(n) is the term where the period of the sequence f(i) begins to repeat. 0
 2, 4, 2, 62, 221, 301, 1062, 860, 21189, 35835, 116119, 317168, 3000313 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE For a(1), the sequence is 1, 2, 3, 5, 11, 2, 3, 5, 11, 2, 3, 5, 11, ... The sequence has period {2, 3, 5, 11} so a(1) = 2. For a(2) see the A112279: 1, 2, 3, 5, 11, 31, 127, 103, 5, 11, 31, 127, 103, 5, 11, ..., . This sequence has a cyclic length of 5, the terms {5, 11, 31, 127, 103} and the first term 5 first appears at the fourth term. MATHEMATICA f[n_] := Block[{k = 1, a}, a[0] = 1; a[i_] := a[i] = Prime[Mod[a[i - 1], 10^n]]; While[t = Table[a[i], {i, 0, k - 1}]; MemberQ[t, a[k]] == False, k++ ]; Flatten[ Position[t, a[k]]][[1]]]; Array[ f, 8] CROSSREFS Cf. A128867. Sequence in context: A263931 A259685 A301460 * A303320 A029589 A121819 Adjacent sequences:  A130169 A130170 A130171 * A130173 A130174 A130175 KEYWORD nonn,more AUTHOR Robert G. Wilson v, May 13 2007 EXTENSIONS a(9)-a(11) from Chai Wah Wu, Sep 26 2019 a(12)-a(13) from Chai Wah Wu, Oct 02 2019 STATUS approved

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Last modified May 13 23:41 EDT 2021. Contains 343868 sequences. (Running on oeis4.)