A342668 Largest prime in the denominator of ratio A341528(n)/A341529(n) (when presented in its lowest terms).

1, 3, 5, 7, 7, 5, 11, 3, 13, 7, 13, 7, 17, 11, 7, 31, 19, 13, 23, 7, 11, 13, 29, 5, 31, 17, 5, 11, 31, 7, 37, 3, 13, 19, 11, 7, 41, 23, 17, 7, 43, 11, 47, 3, 13, 29, 53, 31, 11, 31, 19, 17, 59, 5, 13, 11, 23, 31, 61, 7, 67, 37, 13, 127, 17, 13, 71, 19, 29, 11, 73, 13, 79, 41, 31, 23, 13, 17, 83, 31, 11, 43, 89, 11

Offset: 1

Author

Antti Karttunen, Mar 24 2021

Keywords

• nonn

Links

• Index entries for sequences computed from indices in prime factorization
• Index entries for sequences related to sigma(n)

Crossrefs

Cf. A000203, A003961, A006530, A341527, A341528, A341529, A342667.

Cf. A341628 (same sequence applied onto prime shift array A246278).

Programs

PARI

A003961(n) = { my(f = factor(n)); for (i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); };
A006530(n) = if(n>1, vecmax(factor(n)[, 1]), 1);
A341527(n) = { my(s=A003961(n)); denominator((sigma(s)*n)/(sigma(n)*s)); };
A342668(n) = A006530(A341527(n));

Formula

a(n) = A006530(A341527(n)).