A180169 - OEIS

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A180169

Sigma(A180162(n)), where A180162(n) is the smallest N such that sigma(N) is an n-th power, or 0 if no such N can be found.

1, 3, 4, 8, 1296, 32, 46656, 128, 256, 512, 1024, 362797056, 4096, 8192, 16384, 32768, 65536, 131072, 262144, 524288, 1048576, 2097152, 4194304, 8388608, 16777216, 33554432, 67108864, 134217728, 268435456, 536870912, 1073741824, 2147483648 (list; graph; refs; listen; history; text; internal format)

	OFFSET	`0,2`
	LINKS	`Ray Chandler, Table of n, a(n) for n=1..469`
	FORMULA	`Empirical o.g.f.: (-1-1x+2x^2-1280x^4+2560x^5-46592x^6+93184x^7-362795008x^11+725590016x^12)/(2*x-1)` `Simon Plouffe, Feb. 26 2011.`
	EXAMPLE	`A180162(4)=510 and so A180169(4)=sigma(510)=2^4*3^4.`
	CROSSREFS	`Cf. A065496, A000203, A180162.` `Sequence in context: A096847 A011993 A286125 * A154714 A001695 A019676` `Adjacent sequences: A180166 A180167 A180168 * A180170 A180171 A180172`
	KEYWORD	`easy,nonn`
	AUTHOR	`Walter Kehowski, Aug 14 2010`
	EXTENSIONS	`a(23) onwards from Ray Chandler, Aug 20 2010`
	STATUS	`approved`

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Last modified August 19 01:47 EDT 2017. Contains 290790 sequences.