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.

A134765 Least prime p for which (p-1)/2 - phi(p-1) = n, or 0 if there is no such prime.

This page as a plain text file.
%I A134765 #9 Jul 28 2019 16:38:40
%S A134765 3,7,13,19,41,0,37,31,113,43,101,71,73,67,61,79,97,131,109,103,0,0,0,
%T A134765 191,0,139,677,127,0,419,157,0,193,0,0,151,0,0,0,199,401,683,181,0,
%U A134765 281,0,0,431,0,283,277,0,0,659,461,0,241,211,0,743,313,0,349,271,641,827
%N A134765 Least prime p for which (p-1)/2 - phi(p-1) = n, or 0 if there is no such prime.
%C A134765 The graph of this sequence shows that for n>8 either a(n)=0 or a(n)<=1+n^2. See A098006 for the values of (p-1)/2 - phi(p-1) for odd primes p. Sequence A098047 lists the n for which a(n)=0. A134854(n)=a(2^(n-1)).
%H A134765 T. D. Noe, <a href="/A134765/b134765.txt">Table of n, a(n) for n = 0..10000</a>
%H A134765 T. D. Noe, <a href="http://www.sspectra.com/math/A098006.pdf">Finding primes p for which (p-1)/2 - phi(p-1) = k</a>
%H A134765 T. D. Noe, <a href="http://www.sspectra.com/math/A134765.gif">Graph for n <= 50000</a>
%t A134765 nn=1000; lc=Table[0,{nn}]; Do[p=Prime[n]; r=(p-1)/2-EulerPhi[p-1]; If[0<r<=nn && lc[[r]]==0, lc[[r]]=p], {n,2,PrimePi[1+nn^2]}]; PrependTo[lc,3]
%K A134765 nonn
%O A134765 0,1
%A A134765 _T. D. Noe_, Nov 13 2007, Nov 19 2007