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A340720
Least positive number k such that sigma(k) = n * sigma(k+1).
2
14, 12, 180, 25908120
OFFSET
1,1
EXAMPLE
n | sigma(a(n)) | sigma(a(n)+1)
----+-------------+--------------
1 | 24 | 24
2 | 28 | 14
3 | 546 | 182
4 | 103680000 | 25920000
PROG
(PARI) {a(n) = my(k=1); while(sigma(k)!=n*sigma(k+1), k++); k}
CROSSREFS
KEYWORD
nonn,more,hard
AUTHOR
Seiichi Manyama, Jan 17 2021
STATUS
approved