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 A086698 #4 Sep 04 2025 18:15:05
%S A086698 4,6,9,46,49,69,94,469,626,694,914,934,939,949,4694,4934,4939,9134,
%T A086698 9346,9586,62386,62614,91346,959939,6998339,91439939
%N A086698 Two-sided semiprimes: deleting any number of digits at left or at right, but not both, leaves a semiprime.
%e A086698 a(18)=9134 is a term because 9134, 913,134,34,91,4,9 all are semiprimes.
%t A086698 aspQ[n_]:=Module[{idn=IntegerDigits[n]},AllTrue[Union[FromDigits/@Join[NestList[Rest[#]&,idn,Length[idn]-1],NestList[Most[#]&,idn,Length[idn]-1]]],PrimeOmega[#]==2&]]; Select[Range[10^6],aspQ] (* The program generates the first 24 terms of the sequence. *) (* _Harvey P. Dale_, Sep 04 2025 *)
%K A086698 base,fini,full,nonn,changed
%O A086698 1,1
%A A086698 _Shyam Sunder Gupta_, Jul 28 2003