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 A079672 #16 Mar 17 2024 03:16:10 %S A079672 7,61,73,547,4921,703,5905,44287,6481,398581,478297,3587227,512461, %T A079672 58807,32285041,38742049,530713,290565367,42521761,2615088301, %U A079672 373584043,4780783,3138105961,23535794707,43040161,211822152361,3472494301 %N A079672 Numbers of the form (3^s+1)/(3^r+1) for s > 1, 1 <= r <= s-1. %C A079672 (b^s+1) / (b^r+1) is an integer iff s/r is odd. - Jose Brox (tautocrona(AT)terra.es), Dec 27 2005 %o A079672 (PARI) for(x=2,26, for(y=1,x-1,if(Mod(2^x+1,2^y+1),0,print1((3^x+1)/(3^y+1)",")))) \\ The Mod(2^x+1,2^y+1) is not a bug, since the exponents do not depend on the base in which they are calculated. %Y A079672 Cf. A079665, A079581, A079673. %K A079672 nonn %O A079672 1,1 %A A079672 Jose R. Brox (tautocrona(AT)terra.es), Jan 25 2003