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 A335334 #20 Feb 16 2025 08:34:00
%S A335334 1,6,120,5040,554400,86486400,23524300800,8045310873600,
%T A335334 4070927302041600,3305592969257779200,3074201461409734656000,
%U A335334 4094836346597766561792000,6715531608420337161338880000,12128250084807128913378017280000
%N A335334 Sum of the integers in the reduced residue system of A002110(n).
%C A335334 Sum of the integers up to A002110(n) and coprime to A002110(n).
%C A335334 The sequence gives the sum of row n of A286941(n).
%H A335334 Michael De Vlieger, <a href="/A335334/b335334.txt">Table of n, a(n) for n = 1..196</a>
%H A335334 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Totative.html">Totative</a>.
%F A335334 a(n) = A023896(A002110(n)).
%F A335334 a(n) = A002110(n)*A005867(n)/2 = A070826(n)*A005867(n).
%F A335334 a(n) = (A002110(n)*A038110(n+1)/2)*A058250(n).
%e A335334 For n = 3: A002110(3) = 30, the reduced residue system of 30 is {1, 7, 11, 13, 17, 19, 23, 29}. The sum is a(3) = 120.
%t A335334 n = 15;
%t A335334 A002110 = Drop[FoldList[Times, 1, Prime[Range[n]]], 1];
%t A335334 A005867 = Drop[EulerPhi@FoldList[Times, 1, Prime@Range@n], 1];
%t A335334 A002110*A005867/2
%t A335334 (* Second program: *)
%t A335334 Map[# EulerPhi[#]/2 &, FoldList[Times, Prime@ Range@ 14]] (* _Michael De Vlieger_, Apr 07 2021 *)
%o A335334 (PARI) a(n) = my(P=factorback(primes(n))); P*eulerphi(P)/2; \\ _Michel Marcus_, Jun 02 2020
%Y A335334 Cf. A023896, A002110, A005867, A070826, A038110, A058250, A286941.
%K A335334 nonn
%O A335334 1,2
%A A335334 _Jamie Morken_, Jun 02 2020