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.

A141496 a(0)=1; a(1)=5; a(2)=11; a(n)=a(1)*a(n-1).

Original entry on oeis.org

1, 5, 11, 55, 275, 1375, 6875, 34375, 171875, 859375, 4296875, 21484375, 107421875, 537109375, 2685546875, 13427734375, 67138671875, 335693359375, 1678466796875, 8392333984375, 41961669921875, 209808349609375
Offset: 0

Views

Author

Roger L. Bagula, Aug 10 2008

Keywords

Crossrefs

Programs

  • Mathematica
    Clear[a] a[0] = 1; a[1] = 5; a[2] = 11; a[n_] := a[n] = a[1]*a[n - 1]; Table[a[n], {n, 0, 30}]

Formula

a(n) = 11*5^(n-2) for n>1. a(n) = 5*a(n-1) for n>2. G.f.: (1-14*x^2)/(1-5*x). [Colin Barker, Oct 13 2012]

Extensions

Edited by N. J. A. Sloane, Aug 16 2008

A308124 a(n) = (2 + 7*4^n)/3.

Original entry on oeis.org

3, 10, 38, 150, 598, 2390, 9558, 38230, 152918, 611670, 2446678, 9786710, 39146838, 156587350, 626349398, 2505397590, 10021590358, 40086361430, 160345445718, 641381782870, 2565527131478, 10262108525910, 41048434103638, 164193736414550, 656774945658198, 2627099782632790
Offset: 0

Views

Author

Paul Curtz, Jul 23 2019

Keywords

Comments

Consider A092808 and its differences:
1, 0, 3, 1, 11, 5, 43, 21, 171, ...
-1, 3, -2, 10, -6, 38, -22, 150, ... = b(n).
a(n) is the second bisection of b(n). The first is A047849.
a(n) mod 9 is the period 9 sequence: repeat [3, 1, 2, 6, 4, 5, 0, 7, 8].
b(n) + b(n+1) = A135520(n).

Crossrefs

Programs

  • Mathematica
    LinearRecurrence[{5,-4},{3,10},30] (* Paolo Xausa, Nov 13 2023 *)
    (2+7*4^Range[0,30])/3 (* Harvey P. Dale, Aug 15 2025 *)
  • PARI
    a(n) = (2 + 7*4^n)/3; \\ Stefano Spezia, Jul 23 2019
    
  • PARI
    Vec((3 - 5*x) / ((1 - x)*(1 - 4*x)) + O(x^40)) \\ Colin Barker, Jul 23 2019

Formula

a(n) = 4*a(n-1) - 2 for n=1,2,... , a(0) = 3.
a(n+1) = a(n) + A002042(n).
Binomial transform of A141495(n+1) = 3, 7, 21, ....
From Colin Barker, Jul 23 2019: (Start)
G.f.: (3 - 5*x) / ((1 - x)*(1 - 4*x)).
a(n) = 5*a(n-1) - 4*a(n-2) for n>1.
(End)
a(n+2) = a(n) + 35*A000302(n) for n=0,1,2, ... .

Extensions

a(14)-a(25) from Stefano Spezia, Jul 23 2019
Showing 1-2 of 2 results.