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 A071553 Least x greater than 1 such that x^n == 1 (mod i) for each i=1,2,3,...,n. 0
 2, 3, 7, 5, 61, 11, 421, 13, 121, 71, 27721, 23, 360361, 4159, 841, 307, 12252241, 1121, 232792561, 2393, 4398241, 483209, 5354228881, 4093, 1460244241, 11232649, 61934401, 7598557, 2329089562801, 406639, 72201776446801, 6998993 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Let m(n) = A003418(n) = lcm(1,2,...,n). Then a(n) <= m(n)+1, with equality if and only if n=1 or n is prime. - David W. Wilson, Vladeta Jovovic, Dean Hickerson LINKS MATHEMATICA <n&], Length[f[n, #1]]/#1 0, s++]; s); a[n_?PrimeQ] := LCM @@ Range[n] + 1; a[n_] := a[n] = (km = If[n <= 24, 6, 7]; redu = Reduce[ And @@ Table[ Mod[x^n, n - k] == 1, {k, 0, km}], x, Integers]; candidates = Join @@ Table[ Sort[ List @@ (redu /. C[1] -> c)[[All, 2]]], {c, 0, n}]; First[ Select[ candidates, # > 1 && And @@ Table[ Mod[ #^n, k] == 1, {k, 2, n - km - 1}] & ]]); Table[ Print[a[n]]; a[n], {n, 1, 32}] (* Jean-François Alcover, Jan 13 2012, after PARI for n <= 10 *) PROG (PARI) for(n=1, 12, s=2; while(sum(i=1, n, sign((s^n-1)%i))>0, s++); print1(s, ", ")) CROSSREFS Sequence in context: A069587 A059843 A092927 * A021812 A155891 A234026 Adjacent sequences:  A071550 A071551 A071552 * A071554 A071555 A071556 KEYWORD nonn,nice AUTHOR Benoit Cloitre, May 30 2002 EXTENSIONS Edited by Robert G. Wilson v, Jun 07 2002 More terms from Don Reble, Jun 07 2002 Corrected and extended by Vladeta Jovovic, Jun 09 2002 Corrected and extended by Dean Hickerson, Jun 13 2002 STATUS approved

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Last modified September 18 21:55 EDT 2021. Contains 347537 sequences. (Running on oeis4.)