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%I #22 Jul 14 2021 10:03:37
%S 2,22605,26026,492775589
%N Numbers k such that phi(k) + sigma(k) = reversal(k) + 2.
%C a(5), if it exists, is larger than 10^13.
%C Up to 10^13 the equation phi(k) + sigma(k) = reversal(k) - 2 is satisfied only by k = 26330276.
%e 22605 is in the sequence because phi(22605) = 10880, sigma(22605) = 39744, and 10880 + 39744 = 50622 + 2, where 50622 is the reversal of 22605.
%t Select[Range[493*10^6],EulerPhi[#]+DivisorSigma[1,#]== IntegerReverse[ #]+2&] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Jan 01 2020 *)
%Y Cf. A000010, A000203, A004086.
%Y Cf. A070272, A230004, A230005, A230006, A230019, A136544, A237522.
%K nonn,base,more
%O 1,1
%A _Giovanni Resta_, Feb 08 2014
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