id:A108970 - OEIS Search Results

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Concatenation of triangular number k and its 10's complement is prime.

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1, 3, 21, 91, 561, 861, 903, 1953, 3003, 3741, 5151, 13203, 16653, 17391, 22791, 25651, 29161, 29403, 44253, 45753, 56953, 57291, 64261, 87153, 88831, 97903, 102831, 118341, 128271, 157641, 178503, 179101, 203841, 208981, 216811, 229503 (list; graph; listen)

	OFFSET	`1,2`
	COMMENT	`tri(2^361+201) generates a prime with 436 digits.`
	EXAMPLE	`a(5)=561 because 1000-561 = 439 and 561439 is prime.`
	CROSSREFS	`Sequence in context: A083231 A129755 A059826 this_sequence A069017 A074597 A076207` `Adjacent sequences: A108967 A108968 A108969 this_sequence A108971 A108972 A108973`
	KEYWORD	`easy,nonn,base`
	AUTHOR	`Jason Earls (zevi_35711(AT)yahoo.com), Jul 27 2005`

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Last modified August 29 17:54 EDT 2008. Contains 143238 sequences.

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