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A309541 Representable positive integers n that are not the inverse of their inverse in binary64 (double precision) IEEE 754 floating-point arithmetic (Version where 1 and n*(1/n) are unequal).

%I A309541 #19 Jan 23 2024 20:34:44
%S A309541 49,98,103,107,161,187,196,197,206,214,237,239,249,253,322,347,374,
%T A309541 389,392,394,412,417,425,428,443,474,478,479,491,498,499,501,503,506,
%U A309541 509,561,569,644,685,691,694,725,729,735,737,748,753,765,778,779,784,788,789,797,809,817,823,824,829,833,834,837,841,849,850
%N A309541 Representable positive integers n that are not the inverse of their inverse in binary64 (double precision) IEEE 754 floating-point arithmetic (Version where 1 and n*(1/n) are unequal).
%H A309541 Andrey Zabolotskiy, <a href="/A309541/b309541.txt">Table of n, a(n) for n = 1..10000</a>
%H A309541 Efstratios Gallopoulos, <a href="http://scgroup.hpclab.ceid.upatras.gr/class/SC/Notes/book08.pdf">Scientific Computation I</a>, five terms provided (in Greek) [broken link]
%H A309541 Mark, comment on blog post <a href="http://www.wolter.biz/2008/08/rundungsfehler-im-flash-player/">"Rundungsfehler im Flash Player?"</a>, eight terms (in German)
%H A309541 koDoz, comment in thread <a href="https://scratch.mit.edu/discuss/topic/43137/">"Welche Grenzwerte gelten für Zahlen, Strings usw?"</a>, nine terms (in German)
%o A309541 (Python 2 or Python 3)
%o A309541 for i in range(1,1000):
%o A309541   if i*(1./i) != 1: print(i)
%o A309541 (Fortran)
%o A309541       doubleprecision one, r
%o A309541       integer i
%o A309541       parameter (one=1.0D0)
%o A309541       do 10 i = 1, 500
%o A309541       R = one / dble(i)
%o A309541       if ( R * dble(i) .ne. one) write (*,1000) i
%o A309541 1000  format (i0)
%o A309541 10    continue
%o A309541       end
%o A309541 C _Hugo Pfoertner_, Jan 18 2024
%Y A309541 See A275419 for the n != 1/(1/n) version.
%K A309541 nonn,fini
%O A309541 1,1
%A A309541 _Adam M. Scherlis_, Aug 06 2019