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.

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A064749 a(n) = n*11^n + 1.

Original entry on oeis.org

1, 12, 243, 3994, 58565, 805256, 10629367, 136410198, 1714871049, 21221529220, 259374246011, 3138428376722, 37661140520653, 448795257871104, 5316497670165375, 62658722541234766, 735195677817154577, 8592599484487994108, 100078511642860166659, 1162022718519876379530
Offset: 0

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Author

N. J. A. Sloane, Oct 19 2001

Keywords

Crossrefs

For a(n)=n*k^n+1: A000012 (k=0), A000027(n+1) (k=1), A002064 (k=2), A050914 (k=3), A050915 (k=4), A050916 (k=5), A050917 (k=6), A050919 (k=7), A064746 (k=8), A064747 (k=9), A064748 (k=10), this sequence (k=11), A064750 (k=12).
Cf. A064757.

Programs

  • Magma
    [n*11^n+1: n in [0..20]]; // Vincenzo Librandi, Sep 16 2011
  • Maple
    k:= 11; f:= gfun:-rectoproc({-1 - (k-1)*n + k*n*a(n-1) - (n-1)*a(n) = 0, a(0) = 1, a(1) = k+1}, a(n), remember): map(f, [$0..20]); # Georg Fischer, Feb 19 2021

Formula

a(n) = A064757(n) + 2 for n>=1. - Georg Fischer, Feb 19 2021
G.f.: -(110*x^2-11*x+1)/((x-1)*(11*x-1)^2). - Alois P. Heinz, Feb 19 2021
From Elmo R. Oliveira, May 03 2025: (Start)
E.g.f.: exp(x)*(1 + 11*x*exp(10*x)).
a(n) = 23*a(n-1) - 143*a(n-2) + 121*a(n-3). (End)

A242271 Numbers n such that n*8^n+1 is semiprime.

Original entry on oeis.org

1, 2, 3, 9, 24, 32, 35, 51, 75, 234, 243, 392, 417, 472
Offset: 1

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Author

Vincenzo Librandi, May 10 2014

Keywords

Comments

The semiprimes of this form are: 9, 129, 1537, 1207959553, 113336795588871485128705, 2535301200456458802993406410753, ...
a(15) >= 483. - Hugo Pfoertner, Aug 05 2019

Crossrefs

Cf. similar sequences listed in A242203.

Programs

  • Magma
    IsSemiprime:=func; [n: n in [1..80] | IsSemiprime(s) where s is n*8^n+1];
  • Mathematica
    Select[Range[80], PrimeOmega[# 8^# + 1] == 2 &]

Extensions

a(10)-a(14) from Hugo Pfoertner and Daniel Suteu, Aug 05 2019
Showing 1-2 of 2 results.