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A319068
a(n) is the greatest k such that A000203(k) divides n where A000203 is the sum of divisors of n.
3
1, 1, 2, 3, 1, 5, 4, 7, 2, 1, 1, 11, 9, 13, 8, 7, 1, 17, 1, 19, 4, 1, 1, 23, 1, 9, 2, 13, 1, 29, 25, 31, 2, 1, 4, 22, 1, 37, 18, 27, 1, 41, 1, 43, 8, 1, 1, 47, 4, 1, 2, 9, 1, 53, 1, 39, 49, 1, 1, 59, 1, 61, 32, 31, 9, 5, 1, 67, 2, 13, 1, 71, 1, 73, 8, 37, 4, 45, 1, 79
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
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
Cf. A000203 (sigma), A070982 (the sum of divisors minimum function).
Sequence in context: A002472 A060116 A347120 * A335423 A345011 A345012
KEYWORD
nonn
AUTHOR
Michel Marcus, Sep 09 2018
STATUS
approved