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 A205524 #11 Aug 02 2019 05:26:58 %S A205524 4,8,9,10,14,15,16,21,22,25,26,27,30,32,33,34,35,36,38,39,42,44,45,46, %T A205524 48,49,50,51,52,54,55,57,58,60,62,63,64,65,66,68,69,70,72,74,75,76,77, %U A205524 78,80,81,82,84,85,86,87,90,91,92,93,94,95,96,98,99,100 %N A205524 Numbers n such that gcd(n, sigma(n)) is not equal to sigma(n) mod n. %C A205524 All terms are nonprime numbers. Complement of A205523. %e A205524 Number 25 is in sequence because sigma(25)=31, gcd(25,31) = 1, and 31 mod 25 = 6. %t A205524 Select[Range[100], Mod[GCD[#, DivisorSigma[1, #]] - DivisorSigma[1, #], #] > 0 &] (* _T. D. Noe_, Feb 03 2012 *) %Y A205524 Cf. A000203, A000040, A009194, A054024, A205524, A205525. %K A205524 nonn %O A205524 1,1 %A A205524 _Jaroslav Krizek_, Jan 28 2012 %E A205524 Corrected by _T. D. Noe_, Feb 03 2012