Testwiki:Reference desk/Archives/Mathematics/2013 February 9

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February 9

significance of a series

what is the significance of the series 1, 1, 1, 1, 1, 1, etc. Does it have any special properties? This is A000012 in the online integers database. — Preceding unsigned comment added by 178.48.114.143 (talk) 06:17, 9 February 2013 (UTC)

The OEIS entry for Template:OEIS link lists many properties of this sequence. —Bkell (talk) 18:45, 9 February 2013 (UTC)

For my sandbox

Can somebody calculate the midway point between 500 and 2,200,000,000 please? Please show the calculation as well. This is for a wiki-essay to calculate the largest and smallest religious populations, 2.2 billion being Christians. Thanks Pass a Method talk 20:34, 9 February 2013 (UTC)

What you want is the arithmetic mean, in your case

$\frac{500+2,200,000,000}{2}$

See also http://www.freemathhelp.com/arithmetic-mean.html for some illustrative examples. You might also want to take a look at midpoint. The midpoint is just a special case of an arithmetic mean where you have two terms. -- Toshio Yamaguchi 20:57, 9 February 2013 (UTC)

For something like this I think the geometric mean is more appropriate. For these values you get

$\sqrt{500*2200000000}=1048809$

In other words, about a million. Looie496 (talk) 00:30, 10 February 2013 (UTC)