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A162880 Numbers k such that tau(sigma(k)) is not equal to sigma(tau(k)). 1
2, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 45, 46, 47, 48, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 67, 69, 71, 72, 73, 74, 75, 77, 78, 79, 80 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The complement of A076361, that is, the indices k where A076360(k) is not zero.

LINKS

Table of n, a(n) for n=1..72.

EXAMPLE

a(6)= 8 is in the list because tau(sigma(8))=A062068(8)=4 whereas sigma(tau(8)) = A062069(8) = 7.

PROG

(PARI) is(n)=numdiv(sigma(n))!=sigma(numdiv(n)) \\ Charles R Greathouse IV, Jun 25 2013

CROSSREFS

Cf. A000005, A000203, A076361, A076360.

Sequence in context: A004722 A094798 A326178 * A083792 A083794 A133016

Adjacent sequences:  A162877 A162878 A162879 * A162881 A162882 A162883

KEYWORD

nonn

AUTHOR

Jaroslav Krizek, Jul 16 2009

EXTENSIONS

Edited by R. J. Mathar, Jul 21 2009

STATUS

approved

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Last modified July 15 16:29 EDT 2019. Contains 325049 sequences. (Running on oeis4.)