id:A051445 - OEIS Search Results

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Smallest k such that phi(k) = 2n, or 0 if there is no such k.

+0
4

3, 5, 7, 15, 11, 13, 0, 17, 19, 25, 23, 35, 0, 29, 31, 51, 0, 37, 0, 41, 43, 69, 47, 65, 0, 53, 81, 87, 59, 61, 0, 85, 67, 0, 71, 73, 0, 0, 79, 123, 83, 129, 0, 89, 0, 141, 0, 97, 0, 101, 103, 159, 107, 109, 121, 113, 0, 177, 0, 143, 0, 0, 127, 255, 131, 161, 0, 137 (list; graph; listen)

	OFFSET	`1,1`
	COMMENT	`The zero values are easy to prove because of the bounds on the phi function.` `phi(15)=2*4, so a(4)=15.`
	LINKS	`T. D. Noe, Table of n, a(n) for n=1..10000`
	EXAMPLE	`sigma(4)=7, 4 is the smallest, so a(7)=4.`
	CROSSREFS	`Cf. A002181. For records see A132012, A132115.` `Sequence in context: A114980 A024372 A061390 this_sequence A002181 A073692 A132012` `Adjacent sequences: A051442 A051443 A051444 this_sequence A051446 A051447 A051448`
	KEYWORD	`nonn`
	AUTHOR	`Jud McCranie (j.mccranie(AT)comcast.net)`

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Last modified September 7 15:23 EDT 2008. Contains 143483 sequences.

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