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.
%I A222948 #38 Nov 02 2024 04:08:50
%S A222948 0,1,9,3825,6561,102465,188505,190905,1001385,1556985,3427137,5153577,
%T A222948 5270625,5347881,13658225,14178969,20867625,23828049,27511185,
%U A222948 29400657,48533625,80817009,83406609,89556105,108464265,123395265,127558881,130747689,133861905
%N A222948 Numbers k such that 3*k+1 divides 3^k+1.
%C A222948 This is to 3 as A224486 is to 2
%C A222948 Displayed terms complete up to 200*10^6. - _Joerg Arndt_, Apr 08 2013
%H A222948 Joerg Arndt, <a href="/A222948/b222948.txt">Table of n, a(n) for n = 1..64</a> (all terms <= 10^9)
%F A222948 {n such that (1+A000244(n))/A016777(n) is an integer}.
%e A222948 0 is a term because (3^0+1)/(3*0+1) = 2.
%e A222948 1 is a term because (3^1+1)/(3*1+1) = 1.
%e A222948 9 is a term because (3^9+1)/(3*9+1) = 703.
%o A222948 (PARI) for(n=0,10^9,if((3^n+1)%(3*n+1)==0,print1(n,", "))); /* _Joerg Arndt_, Apr 08 2013 */
%o A222948 /* the following program is significantly faster; it gives terms >=1: */
%o A222948 (PARI) for(n=0, 10^12, my(m=3*n+1); if( Mod(3,m)^n==Mod(-1,m), print1(n, ", ") ) ); /* _Joerg Arndt_, Apr 08 2013 */
%Y A222948 Cf. A224486 (k such that 2*k+1 divides 2^k+1).
%Y A222948 Cf. A000244, A016777.
%K A222948 nonn
%O A222948 1,3
%A A222948 _Jonathan Vos Post_, Apr 07 2013
%E A222948 Terms > 9 from _Joerg Arndt_, Apr 08 2013