id:A050717 - OEIS Search Results

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Inserting a digit '7' between adjacent digits of n makes a prime.

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13, 19, 21, 27, 33, 39, 49, 51, 57, 63, 67, 73, 87, 91, 97, 107, 137, 141, 147, 153, 159, 191, 197, 203, 207, 219, 221, 227, 249, 263, 273, 279, 311, 323, 327, 339, 351, 353, 359, 381, 389, 429, 477, 479, 497, 503, 507, 513, 519, 521, 533, 551, 569, 573, 593 (list; graph; listen)

	OFFSET	`0,1`
	EXAMPLE	`E.g. 477 becomes 4(7)7(7)7 which is prime 47777.`
	CROSSREFS	`Cf. A050674, A050711-A050719.` `Sequence in context: A066469 A119149 A118845 this_sequence A088184 A054986 A071621` `Adjacent sequences: A050714 A050715 A050716 this_sequence A050718 A050719 A050720`
	KEYWORD	`nonn,base`
	AUTHOR	`Patrick De Geest (pdg(AT)worldofnumbers.com), Aug 15 1999.`

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Last modified July 25 07:41 EDT 2008. Contains 142293 sequences.

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