OFFSET
2,1
FORMULA
EXAMPLE
The first terms, alongside a suitable partition, are:
n a(n) Partition
-- ---- ----------------------
2 2 {2}, {1}
3 3 {3}, {1}
4 6 {2, 4}, {1}
5 5 {5}, {1}
6 1 {1, 2, 3}, {6}
7 7 {7}, {1}
8 2 {2, 8}, {1, 4}
9 12 {3, 9}, {1}
10 2 {2, 10}, {1, 5}
11 11 {11}, {1}
12 1 {1, 3, 4, 6}, {2, 12}
13 13 {13}, {1}
14 2 {2, 14}, {1, 7}
15 2 {1, 15}, {3, 5}
PROG
(PARI) a(n) = { my (d=divisors(n), t=vecsum(d), s=[0]); for (i=1, #d, s = setunion(s, [v+d[i] | v <- s]); ); for (i=2, oo, my (r=s[i]/(t-s[i])); if (denominator(r)==1, return (r))) }
CROSSREFS
KEYWORD
nonn
AUTHOR
Rémy Sigrist, Feb 17 2023
STATUS
approved