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 A333291 #20 Dec 01 2024 03:57:27
%S A333291 1,1,3,7,17,21,49,69,105,103,217,173,375,347,435,509,863,601,1243,983,
%T A333291 1271,1265,2217,1449,2575,2225,2935,2573,4549,2241,5601,4609,5195,
%U A333291 4997,6453,4531,9519,7099,8457,6897,13111,6621,15255,11053,11691,12397,20033,11471,20905,14563,19307,17663,28901,16285,26119
%N A333291 a(n) = Sum_{i=1..n, gcd(i,n)=1} i*phi(i) where phi is Euler's totient function A000010.
%H A333291 Seiichi Manyama, <a href="/A333291/b333291.txt">Table of n, a(n) for n = 1..10000</a>
%p A333291 a:= n-> add(`if`(igcd(i, n)=1, i*numtheory[phi](i), 0), i=1..n):
%p A333291 seq(a(n), n=1..55); # _Alois P. Heinz_, Mar 22 2020
%t A333291 a[n_] := Sum[If[CoprimeQ[i, n], i * EulerPhi[i], 0], {i, 1, n}]; Array[a, 100] (* _Amiram Eldar_, Dec 01 2024 *)
%o A333291 (PARI) a(n) = sum(i=1, n, if (gcd(n, i) == 1, i*eulerphi(i))); \\ _Michel Marcus_, Mar 23 2020
%Y A333291 Suggested by A023896 and A319087.
%Y A333291 Cf. A000010, A011755.
%K A333291 nonn,look
%O A333291 1,3
%A A333291 _N. J. A. Sloane_, Mar 22 2020