

A227758


a(n) = sigma(sigma(n))  sigma(n)  n, where sigma(n) = A000203(n) = sum of the divisors of n.


4



1, 1, 0, 3, 1, 10, 0, 1, 8, 11, 5, 16, 3, 22, 21, 15, 4, 1, 3, 34, 10, 33, 13, 84, 24, 28, 23, 36, 13, 93, 0, 9, 43, 32, 41, 15, 15, 70, 25, 104, 13, 114, 3, 96, 45, 77, 29, 52, 26, 15, 72, 21, 13, 186, 68, 184, 49, 86, 49, 252, 27, 94, 43, 63
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OFFSET

1,4


COMMENTS

Conjecture: a(n) = 0 for Mersenne primes (A000668). [This is easily proved: For Mersenne primes n=2^p1, sigma(n)=n+1=2^p, sigma(2^p)=2^(p+1)1, thus a(n)=0.  M. F. Hasler, Jul 30 2013]
a(n) < 0 for numbers n from A227759, a(n) > 0 for numbers n from A227760.
Sequence contains anomalous increased frequency of values 13 (see A227756).


LINKS

Paul Tek, Table of n, a(n) for n = 1..10000


FORMULA

a(n) = A051027(n)  A000203(n)  n.


EXAMPLE

For n = 6; a(n) = sigma(sigma(6))  sigma(6)  6 = 28  12  6 = 10.


CROSSREFS

Cf. A051027, A000203, A000668, A227759, A227760, A227756.
Sequence in context: A128415 A227795 A090479 * A304638 A141903 A010289
Adjacent sequences: A227755 A227756 A227757 * A227759 A227760 A227761


KEYWORD

sign


AUTHOR

Jaroslav Krizek, Jul 26 2013


STATUS

approved



