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Summing with Euler_phi Error

asked 2013-07-10 04:29:53 -0500

david8381 gravatar image

New to sage, having some trouble with summation.

z, k both declared as variables.

sum((euler_phi(k)/k)log(1/(1-2z^k)),k,2,5)

Error: not an integer argument in an arithmetic function (18) If I change it to euler_phi(5)/5 it's fine.

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answered 2013-07-10 04:39:36 -0500

I guess this is because euler_phi does not accept symbolic argument

sage: var('z')
sage: euler_phi(z)
Traceback (most recent call last):
...
PariError: not an integer argument in an arithmetic function (18)

Nevertheless, you can do

sage: sum((euler_phi(k)/k)*log(1/(1-2*z^k)) for k in xrange(2,5))
1/2*log(-1/(2*z^4 - 1)) + 2/3*log(-1/(2*z^3 - 1)) + 1/2*log(-1/(2*z^2 - 1))
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kcrisman gravatar imagekcrisman ( 2013-07-10 04:45:45 -0500 )edit

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Asked: 2013-07-10 04:29:53 -0500

Seen: 52 times

Last updated: Jul 10 '13