A108966 - OEIS

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A108966

Numbers n such that repunit(n) concatenated with its 10's complement is prime; or numbers n such that (1+7*10^n+100^n)/9 is prime.

1, 5, 16, 36, 61, 149, 725, 1104, 1276, 1289, 8575 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,2`
	COMMENTS	`Larger values are only Fermat and Lucas PRPs.`
	EXAMPLE	`a(2)=5 because 10^5-11111 = 88889 and 1111188889 is prime.`
	CROSSREFS	`Cf. A002275.` `Sequence in context: A098404 A190970 A077415 * A184635 A072333 A055232` `Adjacent sequences: A108963 A108964 A108965 * A108967 A108968 A108969`
	KEYWORD	`base,hard,more,nonn`
	AUTHOR	`Jason Earls (zevi_35711(AT)yahoo.com), Jul 26 2005`

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Last modified February 13 12:30 EST 2012. Contains 205469 sequences.