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 A102173 #13 Aug 11 2021 01:25:08
%S A102173 5,9,11,16,22,29,67,72,87,90,94,95,119,123,146,188,323,330
%N A102173 Iccanobirt semiprime indices (3 of 15): Indices of semiprime numbers in A102113.
%F A102173 A102113(a(n)) = A102193(n).
%t A102173 nxt[{a1_,a2_,a3_}]:={a2,a3,a3+FromDigits[Reverse[IntegerDigits[a1]]]+ FromDigits[Reverse[IntegerDigits[a2]]]}; Flatten[Position[Transpose[ NestList[nxt,{0,0,1},200]][[1]],_?(PrimeOmega[#]==2&)]]-1 (* _Harvey P. Dale_, Oct 17 2012 *)
%Y A102173 Cf. A001358, A102113, A102171-A102185, A102193.
%K A102173 nonn,more,less,base
%O A102173 1,1
%A A102173 _Jonathan Vos Post_ and _Ray Chandler_, Dec 31 2004
%E A102173 Offset changed to 1 and a(17)-a(18) from _Jinyuan Wang_, Aug 10 2021