id:A109199 - OEIS Search Results

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Minimal value of k>0 such that n^4 + k^2 is semiprime.

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2, 3, 3, 1, 3, 1, 7, 1, 1, 14, 1, 1, 1, 1, 1, 2, 3, 1, 1, 5, 17, 1, 1, 1, 17, 2, 1, 10, 9, 1, 1, 4, 1, 4, 5, 1, 1, 6, 1, 1, 1, 5, 1, 4, 5, 7, 5, 6, 13, 5, 1, 14, 1, 4, 5, 2, 3, 1, 1, 14, 7, 1, 1, 4, 7, 1, 5, 4, 1, 16, 3, 1, 1, 1, 3, 4, 5, 6, 1, 10, 7, 1, 9, 4, 1, 3, 1, 16, 3, 4, 31, 15, 1, 4, 1, 3, 5, 6, 1, 4 (list; graph; listen)

	OFFSET	`0,1`
	FORMULA	`a(n) = minimal value of k>0 such that n^4 + k^2 is semiprime.`
	EXAMPLE	`a(0) = 2 because 0^4 + 1^2 = 1 is not semiprime, but 0^4 + 2^2 = 4 = 2^2 is.` `a(1) = 3 because 1^4 + 1^2 and 1^4 + 2^2 are not semiprime, but 1^4 + 3^2 = 10 = 2 * 5 is semiprime.` `a(90) = 31 because 90^4 + 31^2 = 65610961 = 13 * 5046997 and for no smaller k>0 is 90^4 + k^2 a semiprime.` `a(100) = 1 because 100^4 + 1^2 = 100000001 = 17 * 5882353.`
	CROSSREFS	`Cf. A001358, A108714, A109197, A109198.` `Sequence in context: A106589 A051911 A106595 this_sequence A087074 A136453 A114104` `Adjacent sequences: A109196 A109197 A109198 this_sequence A109200 A109201 A109202`
	KEYWORD	`easy,nonn`
	AUTHOR	`Jonathan Vos Post (jvospost3(AT)gmail.com), Jun 22 2005`

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Last modified November 27 22:38 EST 2009. Contains 167602 sequences.

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