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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

Table of n, a(n) for n=1..13.

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 June 6 18:59 EDT 2020. Contains 334832 sequences. (Running on oeis4.)