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 A106556 #15 May 01 2023 12:46:14
%S A106556 22,23,33,25,27,35,37,112,55,132,113,172,57,192,133,223,77,173,115,
%T A106556 193,229,231,135,233,237,117,241,175,243,293,137,313,247,195,253,337,
%U A106556 235,259,177,1111,261,341,343,197,267,347,271,1113,295,273,315,279,353
%N A106556 Smallest number formed by concatenating the two factors of a semiprime.
%e A106556 First semiprime is 4; 4 is 2*2 -> 22.
%e A106556 Second semiprime is 6; 6 is 2*3 -> 23.
%e A106556 ...
%e A106556 Eighth semiprime is 22; 22 is 11*2 -> 112 (and not 211).
%t A106556 f[n_]:=Module[{ids=IntegerDigits/@Transpose[FactorInteger[n]][[1]], a,b},a =FromDigits[ Join[ First[ids],Last[ids]]];b=FromDigits[ Join[ Last[ids], First[ids]]];Min[a,b]]; f/@Select[Range[200], PrimeOmega[#] ==2&] (* _Harvey P. Dale_, Jun 20 2011 *)
%K A106556 base,easy,nonn
%O A106556 1,1
%A A106556 _Eric Angelini_, May 09 2005
%E A106556 More terms from _Harvey P. Dale_, Jun 20 2011