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 A106552 Semiprime + (smallest integer obtained by concatenating its two divisors). 2
 26, 29, 42, 35, 41, 50, 58, 134, 80, 158, 146, 206, 92, 230, 172, 269, 126, 224, 170, 250, 287, 293, 200, 302, 311, 194, 323, 260, 329, 380, 228, 406, 341, 290, 359, 448, 350, 377, 296, 1232, 383, 464, 472, 330, 401, 488, 413, 1256, 440, 419, 470, 437, 512 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Robert Israel, Table of n, a(n) for n = 1..10000 EXAMPLE First semiprime is 4; 4 is 2*2; 26=4+22. Second semiprime is 6; 6 is 2*3 (23) or 3*2 (32); 29=6+23. ... Eighth semiprime is 22; 22 is 2*11 (211) or 11*2 (112); 134=22+112. MAPLE count:= 0: R:= NULL: for n from 4 while count < 100 do   F:= ifactors(n)[2];   if nops(F) = 1 and F[1][2]=2 then count:= count+1; R:= R, n + F[1][1]*(1+10^(1+ilog10(F[1][1])))   elif nops(F) = 2 and F[1][2]=1 and F[2][2]=1 then      count:= count+1; p:= F[1][1]; q:= F[2][1];      R:= R, n + min(p+10^(1+ilog10(p))*q, q+10^(1+ilog10(q))*p)   fi od: R; # Robert Israel, Apr 08 2020 MATHEMATICA cc[n_]:=Module[{fi=Transpose[FactorInteger[n]][[1]]}, If[Length[fi]==1, n+FromDigits[Flatten[ IntegerDigits/@{fi, fi}]], n+FromDigits[Flatten[ IntegerDigits/@SortBy[fi, First[IntegerDigits[#]]&]]]]]; cc/@ Select[ Range[300], PrimeOmega[#]==2&](* Harvey P. Dale, Dec 15 2013 *) PROG (PARI) lista(nn) = {for (n=1, nn, if (bigomega(n) == 2, f = factor(n); p = f[1, 1]; q = f[#f~, 1]; print1(n + min(p + q*10^(#Str(p)), q + p*10^(#Str(q))), ", "); ); ); } \\ Michel Marcus, Nov 25 2013 CROSSREFS Cf. A001358, A106553 Sequence in context: A081644 A256619 A055109 * A106550 A304949 A316617 Adjacent sequences:  A106549 A106550 A106551 * A106553 A106554 A106555 KEYWORD base,easy,nonn,look AUTHOR Eric Angelini, May 09 2005 EXTENSIONS Corrected and extended by Harvey P. Dale, Dec 15 2013 a(32) corrected by Robert Israel, Apr 08 2020 STATUS approved

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Last modified October 20 07:41 EDT 2020. Contains 337897 sequences. (Running on oeis4.)