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%I #21 Sep 02 2019 15:26:06
%S 104,147,596,1415,4850,5337,370047,1630622,35020303,120221396,
%T 3954451796,742514284703
%N Composite numbers n such that sigma(n)+6 = sigma(n+6), where sigma=A000203.
%C Complement of A023201 with respect to A015914.
%C Intersection of A015914 and A018252.
%C Below 1000000 there are only 7 such composite numbers, compared with more than 16000 primes.
%C a(13) > 10^13. - _Giovanni Resta_, Jul 11 2013
%D J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 104, p. 37, Ellipses, Paris 2008.
%e n=104, sigma(104)+6 = 210+6 = 216 = sigma(104+6) = sigma(110).
%e a(4) = 1415 = 5*283, 1415+6 = 1421 = 7*7*29:
%e sigma(1415) = 1+5+283+1415 = 1704,
%e sigma(1421) = 1+7+29+49+203+1421 = 1710 = sigma(1415)+6.
%o (PARI) forcomposite(n=9,1e7,if(sigma(n)+6==sigma(n+6),print1(n", "))) \\ _Charles R Greathouse IV_, Feb 14 2013
%Y Cf. A015913-A015917, A023200-A023203, A046133, A001359, A054799.
%K nonn,more
%O 1,1
%A _Labos Elemer_, May 23 2000
%E More terms from _Jud McCranie_, May 25 2000
%E New definition from _Reinhard Zumkeller_, Jan 27 2009
%E Edited by _N. J. A. Sloane_, Jan 31 2009 at the suggestion of _R. J. Mathar_.
%E a(12) from _Giovanni Resta_, Jul 11 2013
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