cp's OEIS Frontend

A342667 Largest prime in the numerator of ratio A341528(n)/A341529(n) (when presented in its lowest terms).

%I A342667 #12 Mar 28 2021 15:53:16
%S A342667 1,2,3,13,5,2,7,2,31,5,11,13,13,7,3,11,17,31,19,13,7,11,23,2,19,13,13,
%T A342667 13,29,2,31,13,11,17,5,31,37,19,13,5,41,7,43,11,31,23,47,11,7,19,17,
%U A342667 13,53,13,11,7,19,29,59,13,61,31,31,1093,13,11,67,17,23,5,71,31,73,37,19,19,7,13,79,11,71,41,83,13
%N A342667 Largest prime in the numerator of ratio A341528(n)/A341529(n) (when presented in its lowest terms).
%C A342667 Equally, largest prime in the denominator of ratio A342661(A003961(n)) / A342662(A003961(n)).
%H A342667 <a href="/index/Pri#prime_indices">Index entries for sequences computed from indices in prime factorization</a>
%H A342667 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>
%F A342667 a(n) = A006530(A341526(n)).
%F A342667 a(n) = A006530(A342664(A003961(n))).
%o A342667 (PARI)
%o A342667 A003961(n) = { my(f = factor(n)); for (i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); };
%o A342667 A006530(n) = if(n>1, vecmax(factor(n)[, 1]), 1);
%o A342667 A341526(n) = { my(s=A003961(n)); numerator((sigma(s)*n)/(sigma(n)*s)); };
%o A342667 A342667(n) = A006530(A341526(n));
%Y A342667 Cf. A000203, A003961, A006530, A064989, A341526, A341528, A341529, A326041, A342661, A342662, A342664, A342668.
%Y A342667 Cf. also A341607.
%K A342667 nonn
%O A342667 1,2
%A A342667 _Antti Karttunen_, Mar 23 2021