The On-Line Encyclopedia of Integer Sequences (OEIS)

A191088 revision #9

A191088

Least number k such that the first n primes are not squares mod k.

3, 5, 43, 43, 67, 67, 163, 163, 163, 163, 163, 163, 74093, 77683, 214037, 214037, 214037, 2004917, 36254563, 51599563, 96295483, 96295483, 114148483, 163520117, 163520117, 261153653, 261153653, 585811843

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OFFSET

1,1

COMMENTS

That is, the first n primes are quadratic non-residues mod k. The first 13 terms are prime. Sequence A191089 is similar, but forces k to be prime.

LINKS

Table of n, a(n) for n=1..28.

MATHEMATICA

Table[k = 2; While[Length[Select[Prime[Range[n]], JacobiSymbol[#, k] == -1 &]] < n, k++]; k, {n, 15}]

PROG

(PARI) q=2; for(k=3, 1e9, forprime(p=2, q, if(kronecker(p, k)>=0, next(2))); print1(k", "); q=nextprime(q+1); k--) \\ Charles R Greathouse IV, Oct 10 2011

CROSSREFS

Cf. A191089.

Sequence in context: A060433 A216085 A219018 * A191089 A199345 A062633

Adjacent sequences: A191085 A191086 A191087 * A191089 A191090 A191091

KEYWORD

nonn

AUTHOR

T. D. Noe, May 25 2011

EXTENSIONS

a(16)-a(28) from Charles R Greathouse IV, Oct 10 2011

STATUS

approved