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 A097393 Emirpimes: numbers n such that n and its reversal are distinct semiprimes. 30
 15, 26, 39, 49, 51, 58, 62, 85, 93, 94, 115, 122, 123, 129, 143, 155, 158, 159, 169, 177, 178, 183, 185, 187, 203, 205, 221, 226, 265, 289, 302, 314, 319, 321, 326, 327, 329, 335, 339, 341, 355, 381, 394, 398, 413, 415, 437, 493, 497, 502, 511, 514, 533 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Computed by Eric W. Weisstein, Aug 13 2004. LINKS Charles R Greathouse IV, Table of n, a(n) for n = 1..10000 Eric Weisstein's World of Mathematics, Emirpimes EXAMPLE 26 is a semiprime, as it is 2 * 13, and so is 62 = 2 * 31. 26 and 62 are therefore both in the sequence. MAPLE isA097393 := proc(n)     local R ;     R := digrev(n) ;     if R <> n then         if numtheory[bigomega](R) = 2 and numtheory[bigomega](n) = 2 then             return true;         else             false;         end if;       else         false;     end if; end proc: for n from 1 to 500 do     if isA097393(n) then         printf("%d, ", n) ;     end if; end do: # R. J. Mathar, Apr 05 2012 MATHEMATICA Select[Range[500], PrimeOmega[#] == 2 && PrimeOmega[FromDigits[Reverse[IntegerDigits[#]]]] == 2 &] (* Alonso del Arte, Oct 08 2012 *) PROG (PARI) rev(n)=subst(Polrev(digits(n)), 'x, 10) issemi(n)=bigomega(n)==2 list(lim)=my(v=List(), r); forprime(p=2, lim\2, forprime(q=2, min(lim\p, p), r=rev(p*q); if(issemi(r)&&r!=p*q, listput(v, p*q)))); Set(v) \\ Charles R Greathouse IV, Jan 27 2015 CROSSREFS Cf. A001358, A097394. Sequence in context: A189045 A032609 A050699 * A050700 A263108 A274182 Adjacent sequences:  A097390 A097391 A097392 * A097394 A097395 A097396 KEYWORD nonn,base AUTHOR STATUS approved

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Last modified October 22 14:44 EDT 2019. Contains 328318 sequences. (Running on oeis4.)