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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A328421 Records in A317993.

Original entry on oeis.org

2, 3, 4, 7, 8, 11, 12, 17, 30, 39, 52, 59
Offset: 1

Views

Author

Jianing Song, Oct 14 2019

Keywords

Comments

Companion sequence of A328420.
It seems that this sequence is infinite (i.e., A317993 is unbounded), but for each n, to really construct a number k such that A317993(k) > a(n) seems impossible.

Examples

			Let (Z/mZ)* be the multiplicative group of integers modulo m. We have (Z/mZ)* = (Z/104Z)* has 8 solutions, namely m = 104, 105, 112, 140, 144, 156, 180, 210; for all k' < 104, (Z/mZ)* = (Z/k'Z)* has fewer than 8 solutions. So A317993(104) = 8 is a term.

Links

Crossrefs

Cf. A317993, A328420.

Programs

  • PARI
    b(n) = if(abs(n)==1||abs(n)==2, 2, my(i=0, k=eulerphi(n), N=floor(exp(Euler)*k*log(log(k^2))+2.5*k/log(log(k^2)))); for(j=k+1, N, if(znstar(j)[2]==znstar(n)[2], i++)); i)
my(t=0); for(k=1, 20000, if(b(k)>t, print1(b(k), ", "); t=b(k))) \\ Warning: program runs for about 30 min
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