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 A261388 a(n) is the length of the longest stretch of consecutive primitive roots of the multiplicative group modulo prime(n). 2
 1, 1, 2, 1, 3, 2, 3, 3, 3, 2, 3, 4, 3, 3, 4, 5, 5, 2, 3, 3, 3, 3, 7, 6, 5, 4, 5, 6, 4, 3, 4, 4, 5, 4, 6, 4, 4, 4, 6, 5, 6, 3, 5, 4, 5, 3, 4, 5, 7, 4, 7, 6, 4, 5, 6, 7, 9, 4, 4, 4, 9, 5, 4, 5, 4, 6, 4, 3, 8, 6, 7, 8, 5, 5, 4, 8, 5, 3, 5, 7, 8, 6, 6, 4, 4, 6, 9, 5, 4, 4, 11, 11, 5, 5, 5, 8, 7, 5, 6 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS Joerg Arndt, Table of n, a(n) for n = 1..9592 (terms for all primes < 10^5) MATHEMATICA a[n_] := 1 + Max[ Join[{0}, Length/@ Select[ Split@ Differences @ PrimitiveRootList @ Prime @ n, #[[1]] == 1 &]]]; Array[a, 99] (* Giovanni Resta, Aug 17 2015 *) PROG (PARI) consec_pr(p)= \\ max number of consecutive primroots {     my( v = vector(p-1) );     my (g = znprimroot(p) );     for (j=1, p-1,  if (gcd(p-1, j)==1, v[lift(g^j)]=1 ) );     my ( m=0, t=0 );     for (j=1, p-1, if ( v[j]==0, t=0 , t+=1; if ( t>m, m=t ); ); );     return(m); } forprime(p=2, 10^3, c=consec_pr(p);  print1( c, ", " ); ); CROSSREFS Cf. A261438 (primes corresponding to records). Sequence in context: A219609 A087825 A263100 * A253281 A029206 A029200 Adjacent sequences:  A261385 A261386 A261387 * A261389 A261390 A261391 KEYWORD nonn AUTHOR Joerg Arndt, Aug 17 2015 STATUS approved

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Last modified June 21 00:15 EDT 2021. Contains 345323 sequences. (Running on oeis4.)