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 A112645 #10 Jan 04 2017 02:39:16
%S A112645 1,8,26,117,2186,145215,1594322
%N A112645 Solutions to abs(sigma(x+1) - sigma(x)) = 2. Divisor sums of x and its neighbor x+1 differ from each other by 2.
%C A112645 Observe that form of 8, 26, 2186 and 1594322 is -1+3^j. Exponents of powers of 3 suitable as number n+1 are as follows: 2, 3, 7, 13, 71, 103. Is the next term 7509466514979724803946715958257546 = -1 + 3^71?
%C A112645 a(8) > 10^13. - _Giovanni Resta_, Jul 11 2013
%e A112645 n = 1594322 = 2*797161 while n+1 = 3^13;
%e A112645 Sigma(n) = 2391486, sigma(n+1) = 2391484.
%t A112645 ta={{0}};Do[s=Abs[DivisorSigma[1, n+1]-DivisorSigma[1, n]]; If[Equal[s, 2], ta=Append[ta, n];Print[n]], {n, 1, 100000000}]; ta=Delete[ta, 1]
%Y A112645 Cf. A000203, A112646, A112647.
%K A112645 more,nonn
%O A112645 1,2
%A A112645 _Labos Elemer_, Sep 28 2005