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A175257
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a(n) is the smallest prime p such that 2^(p-1) == 1 (mod a(1)*...*a(n-1)*p).
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1
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3, 5, 13, 37, 73, 109, 181, 541, 1621, 4861, 9721, 19441, 58321, 87481, 379081, 408241, 2041201, 2449441, 7348321, 14696641, 22044961, 95528161, 382112641, 2292675841, 8024365441, 40121827201, 481461926401
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OFFSET
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1,1
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COMMENTS
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Conjecture: a(n) is the smallest integer k > 1 such that 2^(k-1) == 1 (mod a(0)*...*a(n-1)*k), with a(0) = 1. - Thomas Ordowski, Mar 13 2019
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LINKS
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MATHEMATICA
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i=1; Do[p=Prime[n]; If[Mod[2^(p-1)-1, p*i]==0, Print[p]; i=p*i], {n, 2, 78498}]
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PROG
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(PARI) findprime(prd) = {forprime(p=2, , if (Mod(2, p*prd)^(p-1) == 1, return (p)); ); }
lista(nn) = {my(prd = 1, na); for (n=1, nn, na = findprime(prd); print1(na, ", "); prd *= na; ); } \\ Michel Marcus, Mar 14 2019
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CROSSREFS
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KEYWORD
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more,nonn
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AUTHOR
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EXTENSIONS
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Eliminated a(0)=1 in the definition (empty products equal 1). - R. J. Mathar, Jun 19 2021
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STATUS
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approved
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