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 A136544 #12 Feb 08 2014 22:01:55
%S A136544 3,3997,3999997,168632373,399999999997,3999999999997
%N A136544 Numbers n such that phi(n)+sigma(n)=reversal(n)+3.
%C A136544 Next term of the sequence is greater than 10^9. All semiprimes of the form 4*10^m-3 are in the sequence - the proof is easy. For m=3,6,11,12,13,15,16,18,19,24,38,56,60,... 4*10^m-3 is semiprime. Is it true that 3 is the only prime term in the sequence?
%C A136544 a(7) > 10^13. - _Giovanni Resta_, Feb 08 2014
%e A136544 phi(168632373)+sigma(168632373)=87744384+285492480=373236861+3= reversal(168632373)+3, so 168632373 is in the sequence.
%t A136544 Do[If[DivisorSigma[1,n]+EulerPhi@n==FromDigits@Reverse@IntegerDigits@n+ 3,Print[n]],{n,500000000}]
%Y A136544 Cf. A070272, A230004, A230005, A230006, A230019, A237521, A237522.
%K A136544 base,more,nonn
%O A136544 1,1
%A A136544 _Farideh Firoozbakht_, Jan 20 2008
%E A136544 a(5) from _Giovanni Resta_, Nov 03 2012
%E A136544 a(6) from _Giovanni Resta_, Feb 06 2014