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A186428
sigma(n^2) modulo sigma(n).
0
0, 1, 1, 3, 1, 7, 1, 7, 4, 1, 1, 11, 1, 15, 19, 15, 1, 28, 1, 37, 5, 31, 1, 31, 6, 21, 13, 31, 1, 13, 1, 31, 1, 43, 39, 20, 1, 27, 27, 67, 1, 3, 1, 7, 7, 55, 1, 71, 8, 73, 31, 87, 1, 91, 19, 39, 73, 67, 1, 61, 1, 39, 33, 63, 45, 7, 1, 67, 85, 129, 1, 157, 1, 45, 109, 51, 93, 21, 1, 31, 40, 91, 1, 123, 13, 51, 43, 151, 1, 49, 15, 7, 109, 103, 51, 151, 1, 113, 25, 124, 1, 73, 1, 141, 123, 115, 1, 3, 1, 133, 51, 111, 1, 111, 7, 121, 121
OFFSET
1,4
COMMENTS
a(n)=1 iff n is prime. Apparently a(n)>2 for composite n's.
FORMULA
a(n) = A065764(n) mod A000203(n).
MATHEMATICA
Table[Mod[DivisorSigma[1, n^2], DivisorSigma[1, n]], {n, 200000}]
CROSSREFS
Cf. A000203.
Sequence in context: A316553 A347959 A347963 * A323599 A167515 A140435
KEYWORD
nonn,easy
AUTHOR
Zak Seidov, Mar 06 2011
STATUS
approved