>>> sum(i*i*(-1)**((i % 5) / 4 + (i + 4) % 5 / 4) for i in range(1,2011)) 536926141
On Tue, Jun 15, 2010 at 6:25 PM, superpollo <ute...@esempio.net> wrote: > superpollo ha scritto: > > Peter Otten ha scritto: >> >>> superpollo wrote: >>> >>> goal (from e.c.m.): evaluate >>>> 1^2+2^2+3^2-4^2-5^2+6^2+7^2+8^2-9^2-10^2+...-2010^2, where each three >>>> consecutive + must be followed by two - (^ meaning ** in this context) >>>> >>> >>> from itertools import cycle, izip >>>>>> sum(sign*i*i for sign, i in izip(cycle([1]*3+[-1]*2), range(1, 2011))) >>>>>> >>>>> 536926141 >>> >> >> don't understand it bit i like this a lot! >> > ^^^ > > *but* > > -- > http://mail.python.org/mailman/listinfo/python-list >
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