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%I #10 Jan 04 2017 02:39:25
%S 8,26,2186,1594322,7509466514979724803946715958257546,
%T 13915193059764305937984450503671774362956903094026
%N Special solutions to abs(sigma(x+1) - sigma(x)) = 2 where x + 1 = 3^y.
%C The relevant computed exponents providing -1+3^z solutions for A112645 are 2, 3, 7, 13, 71, 103.
%C The next term, if it exists, is too large to include here. - _N. J. A. Sloane_, Jul 12 2009
%C Contribution from _David Wasserman_, Jul 06 2009: No more terms < 10^86.
%t ta={{0}};Do[s=Abs[DivisorSigma[1, 3^n]-DivisorSigma[1, -1+3^n]]; If[Equal[s, 2], ta=Append[ta, n];Print[ -1+3^n]], {n, 1, 100000000}]; ta=Delete[ta, 1]
%Y Cf. A000203, A112645, A112647.
%K nonn
%O 1,1
%A _Labos Elemer_, Sep 28 2005