id:A075023 - OEIS Search Results

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a(1) = 1, a(n) = the smallest prime divisor of the number C(n) = concatenation of 1,2,3... up to n then reverse up to 1.

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1, 11, 3, 11, 41, 3, 239, 11, 3, 12345678910987654321, 7, 3, 1109, 7, 3, 71, 7, 3, 251, 7, 3, 70607, 7, 3 (list; graph; listen)

	OFFSET	`1,2`
	EXAMPLE	`a(5) = 41 as 123454321= 4141271*271.`
	CROSSREFS	`Cf. A075019, A075020, A075021, A075022, A075024.` `Sequence in context: A110435 A110774 A067063 this_sequence A088262 A110406 A110434` `Adjacent sequences: A075020 A075021 A075022 this_sequence A075024 A075025 A075026`
	KEYWORD	`base,nonn`
	AUTHOR	`Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Sep 01 2002`
	EXTENSIONS	`More terms from Sascha Kurz (sascha.kurz(AT)uni-bayreuth.de), Jan 03 2003`

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Last modified December 18 21:37 EST 2009. Contains 171024 sequences.