cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-5 of 5 results.

A094842 Class numbers associated with entries of A094841.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 22, 22, 79, 107, 107, 311, 432, 487, 665, 665, 692, 1044, 1044, 1044, 1044, 1536, 13909, 13909, 15204, 29351, 29351, 44332, 70877, 70877, 70877, 70877, 149460, 223574, 296475, 296475, 553436, 553436, 553436
Offset: 1

Views

Author

N. J. A. Sloane, Jun 13 2004

Keywords

Crossrefs

Cf. A094841.

A094843 Records in A094841.

Original entry on oeis.org

19, 43, 67, 163, 77683, 1333963, 2404147, 20950603, 36254563, 51599563, 96295483, 114148483, 269497867, 585811843, 52947440683, 71837718283, 229565917267, 575528148427, 1432817816347, 6778817202523, 16501779755323, 30059924764123, 110587910656507, 4311527414591923, 10472407114788067, 22261805373620443, 132958087830686827, 441899002218793387, 2278509757859388307, 5694230275645018963, 9828323860172600203
Offset: 1

Views

Author

N. J. A. Sloane, Jun 13 2004

Keywords

Crossrefs

Cf. A094841.

A001986 Let p be the n-th odd prime. Then a(n) is the least prime congruent to 3 modulo 8 such that Legendre(-a(n), q) = -1 for all odd primes q <= p.

Original entry on oeis.org

19, 43, 43, 67, 67, 163, 163, 163, 163, 163, 163, 222643, 1333963, 1333963, 2404147, 2404147, 20950603, 51599563, 51599563, 96295483, 96295483, 146161723, 1408126003, 3341091163, 3341091163, 3341091163, 52947440683, 52947440683, 52947440683, 193310265163
Offset: 1

Views

Author

Keywords

Comments

Numbers so far are all congruent to 19 mod 24. - Ralf Stephan, Jul 07 2003
All terms are congruent to 19 mod 24. - Jianing Song, Feb 17 2019
Also a(n) is the least prime r congruent to 3 mod 8 such that the first n odd primes are quadratic nonresidues modulo r. Note that r == 3 (mod 8) implies 2 is a quadratic nonresidue modulo r. See A001992 for the case where r == 5 (mod 8). - Jianing Song, Feb 19 2019

References

  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Cf. A001992 (the congruent to 5 mod 8 case), A094851, A094852, A094853.
See A094841, A094842, A094843, A094844 for the case where the terms are not restricted to the primes.

Programs

  • PARI
    isok(p, oddpn) = {forprime(q=3, oddpn, if (kronecker(-p, q) != -1, return (0));); return (1);}
    a(n) = {my(oddpn = prime(n+1)); forprime(p=3, , if ((p%8) == 3, if (isok(p, oddpn), return (p));););} \\ Michel Marcus, Oct 17 2017

Extensions

Revised by N. J. A. Sloane, Jun 14 2004
a(28)-a(30) from Jinyuan Wang, Apr 09 2020

A094847 Let p = n-th odd prime. Then a(n) = least positive integer congruent to 5 modulo 8 such that Legendre(a(n), q) = -1 for all odd primes q <= p.

Original entry on oeis.org

5, 53, 173, 173, 293, 437, 9173, 9173, 24653, 74093, 74093, 74093, 170957, 214037, 214037, 214037, 2004917, 44401013, 71148173, 154554077, 154554077, 163520117, 163520117, 163520117, 261153653, 261153653, 1728061733
Offset: 1

Views

Author

N. J. A. Sloane, Jun 14 2004

Keywords

Comments

With an initial a(0) = 5, a(n) is the least fundamental discriminant D > 1 such that the first n + 1 primes are inert in the real quadratic field with discriminant D. See A094841 for the imaginary quadratic field case. - Jianing Song, Feb 15 2019
All terms are congruent to 5 mod 24. - Jianing Song, Feb 17 2019

Crossrefs

Cf. A094841 (the imaginary quadratic field case), A094842, A094843, A094844.
See A001992, A094851, A094852, A094853 for the case where the terms are restricted to the primes.

Programs

  • PARI
    isok(m, oddpn) = {forprime(q=3, oddpn, if (kronecker(m, q) != -1, return (0));); return (1);}
    a(n) = {oddpn = prime(n+1); m = 5; while(! isok(m, oddpn), m += 8); m;} \\ Michel Marcus, Oct 17 2017

A306218 Fundamental discriminant D < 0 with the least absolute value such that the first n primes p have (D/p) >= 0, negated.

Original entry on oeis.org

4, 8, 15, 20, 24, 231, 264, 831, 920, 1364, 1364, 9044, 67044, 67044, 67044, 67044, 268719, 268719, 3604695, 4588724, 5053620, 5053620, 5053620, 5053620, 60369855, 364461096, 532735220, 715236599, 1093026360, 2710139064, 2710139064, 3356929784, 3356929784
Offset: 1

Views

Author

Jianing Song, Jan 29 2019

Keywords

Comments

a(n) is the negated fundamental discriminant D < 0 with the least absolute value such that the first n primes either decompose or ramify in the imaginary quadratic field with discriminant D. See A241482 for the real quadratic field case.

Examples

			(-231/2) = 1, (-231/3) = 0, (-231/5) = 1, (-231/7) = 0, (-231/11) = 0, (-231/13) = 1, so 2, 5, 13 decompose in Q[sqrt(-231)] and 3, 7, 11 ramify in Q[sqrt(-231)]. For other fundamental discriminants -231 < D < 0, at least one of 2, 3, 5, 7, 11, 13 is inert in the imaginary quadratic field with discriminant D, so a(6) = 231.
		

Crossrefs

Cf. A003657, A232932, A241482 (the real quadratic field case).
A045535 and A094841 are similar sequences.

Programs

  • PARI
    a(n) = my(i=1); while(!isfundamental(-i)||sum(j=1, n, kronecker(-i,prime(j))==-1)!=0, i++); i

Formula

a(n) = A003657(k), where k is the smallest number such that A232932(k) >= prime(n+1).

Extensions

a(26)-a(33) from Jinyuan Wang, Apr 06 2019
Showing 1-5 of 5 results.