OFFSET
1,2
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..10205
Antti Karttunen, Data supplement: n, a(n) computed for n = 1..65537
FORMULA
Sum_{k=1..n} a(k) ~ c * n^2, where c = (1/2) * Product_{p prime} ((p^2-p)/(p^2-nextprime(p)+1)) = 0.73732173..., where nextprime is A151800. - Amiram Eldar, Dec 08 2022
PROG
(PARI) A339905(n) = if(1==n, n, my(f=factor(n)); for(i=1, #f~, f[i, 1] = nextprime(1+f[i, 1])-1); factorback(f));
CROSSREFS
KEYWORD
nonn,mult
AUTHOR
Antti Karttunen, Dec 30 2020
STATUS
approved