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.

A134196 Primes that occur in A126990 only once.

Original entry on oeis.org

19, 37, 43, 53, 67, 83, 97, 109, 157, 173, 211, 223, 229, 251, 257, 263, 277, 283, 307, 313, 349, 353, 367, 373, 383, 401, 443, 457, 463, 479, 503, 557, 563, 571, 587, 593, 607, 613, 631, 643, 653, 677, 683, 719, 727, 733, 751, 829, 853, 859, 877, 883, 911, 929
Offset: 1

Views

Author

Artur Jasinski, Oct 13 2007

Keywords

Links

Crossrefs

Cf. A126990.

Extensions

More terms from Amiram Eldar, Mar 19 2020

A134197 Primes that occur in A126990 twice.

Original entry on oeis.org

3, 7, 13, 23, 31, 47, 61, 73, 89, 103, 113, 131, 139, 151, 167, 181, 193, 199, 233, 241, 271, 293, 317, 337, 359, 389, 409, 421, 433, 449, 467, 491, 509, 523, 547, 577, 601, 619, 647, 661, 691, 709, 743, 761, 773, 797, 811, 823, 839, 863, 887, 919, 941, 953
Offset: 1

Views

Author

Artur Jasinski, Oct 13 2007

Keywords

Comments

It seems, as tested up to prime(100000), that triplicates of primes do not occur in A126990, so this sequence stays the same if defined as either "... in A126990 exactly twice" or "... in A126990 at least twice." - Michel Marcus and R. J. Mathar, Nov 07 2013

Links

Crossrefs

Cf. A126990, A134196.

Programs

  • PARI
    lista(nn) = {last = A126990(1); for (n=2, nn, new = A126990(n); if (new == last, print1(new, ", ")); last = new;);} \\ Michel Marcus, Nov 07 2013

Extensions

More terms from Michel Marcus, Nov 07 2013

A133261 Union of A134196 and A134197 : A126990 with duplicates removed.

Original entry on oeis.org

3, 7, 13, 19, 23, 31, 37, 43, 47, 53, 61, 67, 73, 83, 89, 97, 103, 109, 113, 131, 139, 151, 157, 167, 173, 181, 193, 199, 211, 223, 229, 233, 241, 251, 257, 263, 271, 277, 283, 293, 307, 313, 317, 337, 349, 353, 359, 367, 373, 383, 389, 401, 409, 421, 433, 443
Offset: 1

Views

Author

Artur Jasinski, Oct 15 2007

Keywords

Crossrefs

Cf. A134196, A134197, A126990.

Programs

  • Mathematica
    << NumberTheory`NumberTheoryFunctions` a = {}; Do[AppendTo[a, PreviousPrime[Sqrt[(Prime[ x - 1])*(Prime[x + 1])]]], {x, 2, 300}]; Union[a]

A134240 Numbers which occur in A105399 but not in A126990.

Original entry on oeis.org

79, 127, 163, 331, 379, 397, 439, 487, 499, 541, 673, 701, 739, 757, 769, 787, 907, 937, 947, 967, 977, 991, 1009, 1103, 1123, 1163, 1187, 1213, 1249, 1367, 1399, 1523, 1549, 1567, 1579, 1597, 1753, 1801
Offset: 1

Views

Author

Artur Jasinski, Oct 15 2007

Keywords

Crossrefs

Cf. A105399, A134196, A134197, A126990.

A126991 Prime preceding the geometric mean of prime(n-2) and prime(n+2).

Original entry on oeis.org

3, 5, 7, 11, 13, 19, 19, 23, 29, 31, 37, 43, 47, 47, 53, 61, 61, 67, 73, 79, 83, 89, 89, 97, 101, 103, 113, 113, 113, 113, 137, 139, 139, 149, 157, 157, 167, 167, 173, 181, 181, 181, 199, 199, 211, 211, 211, 229, 233, 239, 241, 241, 251, 257, 263, 271, 271, 281
Offset: 3

Views

Author

Artur Jasinski, Jan 01 2007

Keywords

Crossrefs

Cf. A126990, A126992, A124662.

Programs

  • Mathematica
    << NumberTheory`NumberTheoryFunctions` a = {}; Do[AppendTo[a,PreviousPrime[Sqrt[(Prime[x - 2])*(Prime[x + 2])]]], {x, 3, 100}]; a
Table[NextPrime[GeometricMean[{Prime[n-2],Prime[n+2]}],-1],{n,3,60}] (* Harvey P. Dale, May 14 2015 *)
  • PARI
    A126991(n)={ n=sqrtint(prime(n-2)*prime(n+2)); if(0==n%2, n--); while(!isprime(n), n-=2); n } /* then vector(50,n,A126991(n+2)) displays a list of values ; t=3;forprime(p=2,999, while(A126991(t)A126991(t)>p,print(p))) prints primes 2,17,41,59,... not in this sequence */ \\ M. F. Hasler, Jun 14 2007

Extensions

Edited by M. F. Hasler, Jun 14 2007
Showing 1-5 of 5 results.

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