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 1-3 of 3 results.

A095103 4k+3 primes whose Legendre-vector is not valid Dyck-path.

Original entry on oeis.org

19, 43, 67, 107, 127, 139, 163, 179, 211, 223, 227, 283, 307, 331, 347, 367, 379, 443, 463, 467, 487, 491, 499, 523, 547, 571, 587, 619, 631, 643, 683, 691, 727, 739, 787, 811, 823, 827, 859, 883, 907, 947, 967, 1019, 1051, 1087, 1123, 1163
Offset: 1

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Author

Antti Karttunen, Jun 01 2004

Keywords

Crossrefs

Intersection of A000040 and A095101. Complement of A095102 in A002145.
Cf. A095093, A095108 (diving indices).

Programs

  • Mathematica
    L = {}; Do[p = Prime[k]; If[Mod[p, 4] == 3 && Min[Table[Sum[JacobiSymbol[n, p], {n, 0, m}], {m, 0, p - 1}]] < 0, L = Append[L, p]], {k, 1, 192}]; L (* From Jonathan Sondow, Oct 25 2011 *)
  • PARI
    isok(m) = {my(s=0); if(m%4==3&&isprime(m), for(i=1, m-1, if((s+=kronecker(i, m))<0, return(1)))); 0; } \\ Jinyuan Wang, Jul 20 2020
    
  • Sage
    def A095103_list(n) :
        def is_Motzkin(n, k):
            s = 0
            for i in (1..k) :
                s += jacobi_symbol(i, n)
                if s < 0 : return false
            return true
        P = filter(is_prime, range(n+1)[3::4])
        return filter(lambda m: not is_Motzkin(m, m//2), P)
    A095103_list(1163) # Peter Luschny, Aug 08 2012

Formula

a(n) = 4*A095273(n) + 3.

A095104 Diving index of the n-th 4k+3 prime (A002145(n)).

Original entry on oeis.org

0, 0, 0, 3, 0, 0, 3, 0, 0, 3, 0, 0, 0, 0, 7, 7, 0, 3, 0, 3, 0, 11, 0, 0, 3, 13, 61, 0, 0, 0, 0, 3, 3, 0, 3, 7, 0, 45, 3, 0, 0, 0, 0, 7, 7, 35, 0, 7, 35, 3, 0, 3, 3, 0, 3, 15, 0, 0, 3, 15, 3, 0, 0, 7, 3, 0, 45, 3, 0, 0, 3, 3, 7, 7, 0, 3, 0, 3, 0, 3, 0, 0, 7, 7, 0, 0, 0, 67, 0, 0, 3, 0
Offset: 1

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Author

Antti Karttunen, Jun 01 2004

Keywords

Comments

Diving index of an odd number n is the first integer u > 1 where Sum_{i=1..u} J(i/n) results -1 and zero if never. Here J(i/n) is Jacobi symbol of i and n, which reduces to a Legendre symbol L(i/n) when n is a prime.

Crossrefs

a(n)=A095105(n)+1 modulo A002145(n). Cf. A095106, A095108 (same sequence with zeros removed), A095269.

A095271 Diving index of A095101(n).

Original entry on oeis.org

3, 3, 10, 3, 3, 10, 7, 3, 7, 7, 3, 8, 8, 3, 11, 3, 34, 8, 19, 3, 10, 13, 61, 3, 7, 3, 7, 8, 3, 10, 3, 32, 7, 3, 58, 7, 3, 45, 3, 7, 3, 13, 31, 3, 8, 7, 3, 10, 7, 35, 3, 8, 7, 35, 3, 14, 8, 3, 13, 22, 3, 8, 3, 103, 7, 15, 3, 7, 40, 3, 7, 15, 55, 3, 113, 31, 3, 7, 13, 3, 118
Offset: 1

Views

Author

Antti Karttunen, Jun 01 2004

Keywords

Crossrefs

Formula

a(n) = A095269(A095275(n)). See comments at A095269.
Showing 1-3 of 3 results.