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A246487 Numbers x such that sigma(x) + sigma(R(x)) = sigma(x + R(x)), where R(x) is the digit reversal of x and sigma(x) is the sum of the divisors of x.

%I A246487 #14 Jul 27 2017 15:44:14
%S A246487 78,87,104,401,1144,2072,2178,2702,4411,7038,7348,7878,8307,8437,8712,
%T A246487 8787,11144,11544,12584,15834,20710,20913,21476,21978,22164,26070,
%U A246487 31902,43851,44111,44511,46122,48521,66649,67412,87912,94666,102786,122584,122784,126984
%N A246487 Numbers x such that sigma(x) + sigma(R(x)) = sigma(x + R(x)), where R(x) is the digit reversal of x and sigma(x) is the sum of the divisors of x.
%H A246487 Paolo P. Lava, <a href="/A246487/b246487.txt">Table of n, a(n) for n = 1..100</a>
%e A246487 x = 15834 -> R(x) = 43851 and sigma(15834) + sigma(43851) = 40320 + 59904 = 100224 = sigma(15834 + 43851)= sigma(59685).
%p A246487 with(numtheory): P:=proc(q) local a,b,k,n;
%p A246487 for n from 1 to q do a:=n; b:=0;
%p A246487 for k from 1 to ilog10(n)+1 do b:=10*b+(a mod 10); a:=trunc(a/10);
%p A246487 od; if sigma(n)+sigma(b)=sigma(n+b) then print(n); fi;
%p A246487 od; end: P(10^6);
%t A246487 Select[Range[130000],DivisorSigma[1,#]+DivisorSigma[1,IntegerReverse[#]] == DivisorSigma[1,#+IntegerReverse[#]]&] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Jul 27 2017 *)
%o A246487 (PARI) isok(n) = rn = subst(Polrev(digits(n)), x, 10); sigma(n + rn) == sigma(n) + sigma(rn); \\ _Michel Marcus_, Aug 29 2014
%Y A246487 Cf. A000203, A004086, A211223.
%K A246487 nonn,base,easy
%O A246487 1,1
%A A246487 _Paolo P. Lava_, Aug 27 2014