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 A105852 #19 Apr 25 2023 14:14:15 %S A105852 1,3,4,7,6,3,8,6,4,0,3,1,5,6,6,4,0,3,2,6,5,0,6,6,4,6,4,2,3,0,5,0,3,0, %T A105852 3,1,2,6,2,0,6,6,8,3,6,0,3,7,3,3,0,8,0,3,0,3,8,0,6,6,8,6,5,1,3,0,5,0, %U A105852 6,0,0,6,2,6,7,5,6,6,8,6,4,0,3,8,0,6,3,0,0,0,4,6,2,0,3,0,8,0,3,1,3,0,5,3,3 %N A105852 a(n) = sigma(n) mod 9. %C A105852 If gcd(m,n) = 1 then a(m*n) = (a(m) * a(n)) mod 9. - _Robert Israel_, Sep 14 2014 %H A105852 Robert Israel, <a href="/A105852/b105852.txt">Table of n, a(n) for n = 1..10000</a> %F A105852 a(n) = A010878(A000203(n)). - _Michel Marcus_, Sep 14 2014 %p A105852 seq(numtheory:-sigma(n) mod 9, n=1..1000); # _Robert Israel_, Sep 14 2014 %t A105852 Mod[DivisorSigma[1, Range[100]], 9] (* _Wesley Ivan Hurt_, Apr 25 2023 *) %o A105852 (PARI) a(n)=sigma(n)%9 %Y A105852 Cf. A000203, A010878, A190998 (digital root of sigma(n)). %K A105852 easy,nonn %O A105852 1,2 %A A105852 _Shyam Sunder Gupta_, May 05 2005 %E A105852 Name corrected and keyword base removed by _Michel Marcus_, Sep 14 2014