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A070610
Number of positive integers k such that sigma(k) divides sigma(n).
2
1, 2, 2, 2, 3, 6, 3, 3, 2, 5, 6, 5, 3, 10, 10, 3, 5, 4, 3, 8, 5, 9, 10, 12, 3, 8, 5, 8, 5, 18, 5, 4, 13, 7, 13, 4, 2, 12, 8, 10, 8, 19, 3, 15, 6, 18, 13, 7, 3, 5, 18, 5, 7, 21, 18, 21, 7, 10, 12, 27, 4, 19, 6, 2, 15, 26, 3, 13, 19, 26, 18, 6, 2, 7, 7, 8, 19, 27, 7, 9, 2, 13, 15, 14, 13, 9
OFFSET
1,2
FORMULA
a(n) = A074754(A000203(n)). - Antti Karttunen, Nov 17 2017
PROG
(PARI) for(n=1, 150, print1(sum(i=1, 10*n, if((sigma(n))%(sigma(i)), 0, 1)), ", "))
(PARI) A070610(n) = { my(s=sigma(n)); sum(k=1, s, !(s%sigma(k))); }; \\ Antti Karttunen, Nov 17 2017
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, May 13 2002
EXTENSIONS
Offset corrected, name edited by Antti Karttunen, Nov 17 2017
STATUS
approved