|
|
A168127
|
|
Numbers k such that Sum_{j=1..k} sigma(j) / sigma(k) is an integer.
|
|
4
|
|
|
1, 3, 29, 365, 1225, 81595, 86249, 185699, 582917, 11413204, 16646745763, 311408527843, 709342670921, 881267828693
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
COMMENTS
|
|
|
LINKS
|
|
|
EXAMPLE
|
29 is in the sequence because A024916(29) / A000203(29) = 690 / 30 = 23 is an integer.
|
|
PROG
|
(PARI) m=0; for(k=1, 11413204, s=sigma(k); m=m+s; if(m%s==0, print1(k ", "))) \\ Donovan Johnson, Oct 16 2013
(PARI) isok(k) = (sum(j=1, k, sigma(j)) % sigma(k)) == 0; \\ Michel Marcus, Feb 19 2020
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,more
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|