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 A106554 #24 Feb 06 2024 14:27:21
%S A106554 22,23,33,25,27,35,37,211,55,213,311,217,57,219,313,223,77,317,511,
%T A106554 319,229,231,513,323,237,711,241,517,243,329,713,331,247,519,253,337,
%U A106554 523,259,717,1111,261,341,343,719,267,347,271,1113
%N A106554 Concatenation of the two prime divisors of a semiprime, smallest divisor first.
%C A106554 Concatenation of the divisors starting with the largest one leads to another sequence.
%H A106554 Michael De Vlieger, <a href="/A106554/b106554.txt">Table of n, a(n) for n = 1..10000</a>
%F A106554 a(n) = A037276(A001358(n)). - _R. J. Mathar_, Oct 29 2012
%e A106554 First semiprime is 4; 4 is 2*2 -> 22.
%e A106554 Second semiprime is 6; 6 is 2*3 -> 23.
%e A106554 Third semiprime is 9; 9 is 3*3 -> 33.
%e A106554 Fourth semiprime is 10; 10 is 2*5 -> 25.
%p A106554 read("transforms") :
%p A106554 A106554 := proc(n)
%p A106554 A037276(A001358(n)) ;
%p A106554 end proc: # _R. J. Mathar_, Oct 29 2012
%t A106554 FromDigits@ Flatten[IntegerDigits@ Table[#1, {#2}] & @@@ FactorInteger@ #] & /@ Select[Range@ 144, PrimeOmega@ # == 2 &] (* _Michael De Vlieger_, Oct 01 2015 *)
%o A106554 (PARI) do(x)=my(v=List()); forprime(p=2, sqrt(x), forprime(q=p, x\p, listput(v, [p*q, eval(Str(p, q))]))); Vec(apply(u->u[2], vecsort(v, 1))) \\ _Charles R Greathouse IV_, Sep 30 2015
%Y A106554 Cf. A106550, A084126, A084127, A001358.
%K A106554 base,easy,nonn
%O A106554 1,1
%A A106554 _Eric Angelini_, May 09 2005
%E A106554 More terms from _Reinhard Zumkeller_, May 19 2005
%E A106554 Data corrected by _Giovanni Teofilatto_ and _Altug Alkan_, Oct 01 2015