id:A119665 - OEIS Search Results

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Sign in the term (2q +/- 1) for triangular numbers of the form q * (2q +/- 1) where both factors are primes (or prime powers).

+0
1

-1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1, 1, -1, 1, -1, -1, 1, -1, -1, 1, -1 (list; graph; listen)

	OFFSET	`0,1`
	EXAMPLE	`a(6) = +1 since 21 = 37 and 7 = 23 + 1.` `a(7) = -1 since 28 = 47 and 7 = 24 - 1.` `a(8) = +1 since 36 = 49 and 9 = 24 + 1.`
	CROSSREFS	`Cf. A068443.` `Sequence in context: A015435 A014676 A015343 this_sequence A016300 A016126 A016068` `Adjacent sequences: A119662 A119663 A119664 this_sequence A119666 A119667 A119668`
	KEYWORD	`sign`
	AUTHOR	`Greg Huber (huber(AT)alum.mit.edu), Jul 28 2006`

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Last modified November 29 12:46 EST 2009. Contains 167659 sequences.