OFFSET
1,3
COMMENTS
Sándor names this function the sum-of-divisors maximum function and remarks that this function is well-defined, since a(n) can be at least 1, and cannot be greater than n.
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..16384
Antti Karttunen, Data supplement: n, a(n) computed for n = 1..65537
József Sándor, The sum-of-divisors minimum and maximum functions, Research Report Collection, Volume 8, Issue 1, 2005. See pp. 3-4.
FORMULA
a(p+1) = p, for p prime. See Sándor Theorem 2 p. 4.
PROG
(PARI) a(n) = {forstep (k=n, 1, -1, if ((n % sigma(k)) == 0, return (k)); ); }
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Marcus, Sep 09 2018
STATUS
approved