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 A081653 #14 Aug 10 2025 17:01:51
%S A081653 1,1,1,1,1,2,1,2,1,1,2,1,1,1,1,1,2,1,1,2,1,4,1,1,1,2,1,2,1,1,2,5,1,1,
%T A081653 2,1,1,1,2,1,1,2,1,1,1,1,1,1,1,1,2,7,1,1,2,11,1,1,2,1,1,2,1,5,1,1,1,1,
%U A081653 1,1,1,1,2,1,1,1,2,1,1,1,1,1,1,2,1,1,1,16,1,1,1,1,1,1,2,1,2,1,2,1,2,1,2,5,1
%N A081653 Greatest common divisor of sums of decimal digits of n and of n-th prime.
%F A081653 a(n) = GCD(A007953(n), A007605(n)).
%e A081653 a(8) = GCD(A007953(8), A007953(A000040(8))) = GCD(8, A007953(19)) = GCD(8,1+9) = GCD(4*2,5*2) = 2.
%t A081653 A081653[n_Integer]:=GCD[Plus@@IntegerDigits[n],Plus@@IntegerDigits[Prime[n]]]; Table[A081653[n],{n,105}] (* _Enrique Pérez Herrero_, Aug 07 2010 *)
%Y A081653 Cf. A000040, A007953, A007605, A081652, A066750.
%K A081653 nonn,base,easy
%O A081653 1,6
%A A081653 _Reinhard Zumkeller_, Mar 25 2003