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A355598
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a(1) = 3. For n > 1, a(n) = smallest prime q such that q^(a(n-1)-1) == 1 (mod a(n-1)^2).
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5
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3, 17, 131, 659, 503, 9833, 49603, 327317, 13900147, 144229223, 5872276013
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OFFSET
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1,1
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COMMENTS
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Is this overall an increasing sequence or does it enter a cycle?
The sequence decreases for the first time at n = 5.
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LINKS
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MATHEMATICA
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sp[n_]:=Module[{p=2}, While[PowerMod[p, n-1, n^2]!=1, p=NextPrime[p]]; p]; NestList[sp, 3, 8] (* Harvey P. Dale, Jul 23 2023 *)
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PROG
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(PARI) seq(start, terms) = my(x=start, i=1); print1(start, ", "); while(1, forprime(q=1, , if(Mod(q, x^2)^(x-1)==1, print1(q, ", "); x=q; i++; if(i >= terms, break({2}), break))))
seq(3, 20) \\ Print initial 20 terms of sequence
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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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