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 A107473 #12 Aug 04 2025 11:47:22
%S A107473 2,3,5,3,9,4,13,3,5,7,21,4,25,10,23,3,33,4,37,7,11,16,45,4,9,19,5,10,
%T A107473 57,19,61,3,53,25,59,4,73,28,21,7,81,9,85,16,23,34,93,4,13,7,83,19,
%U A107473 105,4,19,10,31,43,117,19,121,46,11,3,113,43,133,25,113,47,141,4,145,55,23,28
%N A107473 Sum of numerator and denominator of Product_{p|n, p prime} (1 - 1/p).
%F A107473 a(n) = A076511(n) + A076512(n). - _Michel Marcus_, Aug 16 2019
%e A107473 a(12) = 4 = 1+3 because (1 - 1/2)(1 - 1/3) = 1/3.
%p A107473 a:=proc(n) local b,ct,f; with(numtheory): b:=convert(factorset(n),list): ct:=nops(b): f:=simplify(product(1-1/b[j],j=1..ct)):numer(f)+denom(f) end: seq(a(n),n=1..100); # _Emeric Deutsch_, May 28 2005
%Y A107473 Cf. A076511, A076512.
%K A107473 nonn
%O A107473 1,1
%A A107473 _Leroy Quet_, May 27 2005
%E A107473 More terms from _Emeric Deutsch_, May 28 2005