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 1-2 of 2 results.

A264011 Exponents n such that 2^(2*n+1) - 3*2^n - 1 (A195461) is prime.

Original entry on oeis.org

2, 3, 4, 5, 8, 16, 27, 28, 33, 36, 48, 66, 90, 112, 508, 1036, 1041, 1560, 2208, 2668, 4388, 6097, 6517, 11353, 17284, 22385, 24740, 29805, 77188, 135219, 199237
Offset: 1

Views

Author

Fabrice Lavier, Jan 03 2016

Keywords

Comments

Obtained using a Lucas-Lehmer-type test due to Williams.
Next term > 200000.

Links

Crossrefs

Cf. A195461.

Programs

  • PARI
    for(n=1,10^9,if(ispseudoprime(2^(2*n+1) - 3*2^n - 1),print1(n,", "))); \\ Joerg Arndt, Apr 08 2016

A195460 a(n) = 2^(2*n+1) - 3*2^n - 1.

Original entry on oeis.org

1, 19, 103, 463, 1951, 7999, 32383, 130303, 522751, 2094079, 8382463, 33542143, 134193151, 536821759, 2147385343, 8589737983, 34359345151, 137438167039, 549754241023, 2199020109823, 8796086730751, 35184359505919, 140737463189503
Offset: 1

Views

Author

Brad Clardy, Sep 18 2011

Keywords

Comments

Binary numbers of the form (n)00(m) where n and m are the number of 1's, m is the index and n=m-1.

Examples

			First few terms in binary are 1, 10011, 1100111, 111001111, 11110011111, 1111100111111.

Links

Crossrefs

Cf. A052539, A103897, A195461 (prime values).

Programs

  • Magma
    [2*4^n-3*2^n-1: n in [1..23]]; // Bruno Berselli, Sep 19 2011
  • PARI
    a(n)=1<<(2*n+1)-3<Charles R Greathouse IV, Sep 19 2011

Formula

a(n) = 2*a(n-1)+A052539(n) = a(n-1)+A103897(n) for n>1.
G.f.: x*(1+12*x-16*x^2)/((1-x)*(1-2*x)*(1-4*x)). - Bruno Berselli, Sep 19 2011
Showing 1-2 of 2 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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