id:A128428 - OEIS Search Results

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Number of unique prime factors of n^2+1.

+0
1

1, 1, 2, 1, 2, 1, 2, 2, 2, 1, 2, 2, 3, 1, 2, 1, 3, 2, 2, 1, 3, 2, 3, 1, 2, 1, 3, 2, 2, 2, 3, 2, 3, 2, 2, 1, 3, 2, 2, 1, 2, 2, 3, 2, 2, 2, 4, 2, 2, 2, 2, 2, 3, 1, 3, 1, 3, 2, 2, 2, 2, 2, 3, 2, 2, 1, 3, 2, 2, 2, 2, 3, 4, 1, 3, 2, 3, 2, 2, 2, 3, 2, 4, 1, 2, 2, 3, 2, 3, 1, 3, 2, 3, 1, 2, 2, 3, 3, 3 (list; graph; listen)

	OFFSET	`1,3`
	FORMULA	`a(n) = number of unique prime factors of n^2+1`
	EXAMPLE	`a(3)=2 because 3^2+1=2*5`
	MATHEMATICA	`a[n_]:=Length[FactorInteger[n^2 + 1]]`
	CROSSREFS	`Sequence in context: A036430 A163377 A163109 this_sequence A056171 A076755 A106490` `Adjacent sequences: A128425 A128426 A128427 this_sequence A128429 A128430 A128431`
	KEYWORD	`nonn`
	AUTHOR	`Kent Horvath (kenthorvath(AT)gmail.com), May 10 2007`

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Last modified December 20 16:54 EST 2009. Contains 171081 sequences.

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