id:A047818 - OEIS Search Results

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a(n) is the least number m such that A002313(n)*m - 1 is a square.

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1, 1, 2, 1, 5, 1, 2, 10, 2, 10, 13, 5, 1, 10, 2, 10, 13, 5, 37, 2, 34, 1, 50, 34, 17, 1, 25, 13, 10, 65, 2, 41, 65, 53, 5, 29, 34, 10, 1, 50, 2, 74, 10, 26, 5, 85, 106, 5, 25, 13, 1, 10, 26, 2, 61, 37, 34, 17, 5, 1, 26, 13, 170, 10, 2, 5, 130, 58, 125, 106, 73, 130, 50, 26, 170 (list; graph; listen)

	OFFSET	`1,3`
	COMMENT	`A002313 has the 4k+1 and 4k+2 primes.` `Related to Stormer numbers.`
	REFERENCES	`J. Todd, A problem on arc tangent relations, Amer. Math. Monthly, 56 (1949), 517-528.`
	FORMULA	`a(n) = ([A002314(n-1)]^2 + 1) / A002313(n)`
	EXAMPLE	`a(3) = 2 because A002313(3)=13 and 13*2-1 = 5^2.`
	CROSSREFS	`Cf. A002313, A002314, A005528.` `Sequence in context: A113767 A157334 A132601 this_sequence A055972 A079168 A055205` `Adjacent sequences: A047815 A047816 A047817 this_sequence A047819 A047820 A047821`
	KEYWORD	`nonn`
	AUTHOR	`N. J. A. Sloane (njas(AT)research.att.com).`
	EXTENSIONS	`Edited by Don Reble (djr(AT)nk.ca), Apr 13 2006`

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Last modified November 25 08:46 EST 2009. Contains 167481 sequences.

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