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 A220979 #18 Feb 14 2024 02:21:06
%S A220979 11,12851,9384251,6054921251,3808599606251,2383422998031251,
%T A220979 1490020755615156251,931310653778075781251,582075119020843503906251,
%U A220979 363797694444713592519531251,227373652160169124603222656251,142108544241637027263641113281251
%N A220979 a(n) = 5^(4n+2) - 5^(3n+2) + 3 * 5^(2n+1) - 5^(n+1) + 1: the left Aurifeuillian factor of 5^(10n+5) - 1.
%C A220979 The corresponding right Aurifeuillian factor is A220980.
%H A220979 Wikipedia, <a href="http://en.wikipedia.org/wiki/Cunningham_project">Cunningham Project</a>
%H A220979 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (781,-101530,2538250,-12203125,9765625).
%F A220979 Aurifeuillian factorization: 5^(10n+5) - 1 = (5^(2n+1) - 1) * a(n) * A220980(n).
%F A220979 G.f.: -(4296875*x^4+2662500*x^3+464450*x^2+4260*x+11) / ((x-1)*(5*x-1)*(25*x-1)*(125*x-1)*(625*x-1)). - _Colin Barker_, Jan 03 2013
%t A220979 Table[5^(4n+2) - 5^(3n+2) + 3 * 5^(2n+1) - 5^(n+1) + 1, {n, 0, 30}]
%o A220979 (PARI) a(n)=5^(4*n+2)-5^(3*n+2)+3*5^(2*n+1)-5^(n+1)+1 \\ _Charles R Greathouse IV_, Sep 28 2015
%Y A220979 Cf. A092440, A085601, A220978, A198410, A220980-A220990.
%K A220979 nonn,easy
%O A220979 0,1
%A A220979 _Stuart Clary_, Dec 27 2012