id:A138928 - OEIS Search Results

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Indices n such that A020501(n) = Phi[n](-2) is prime, where Phi is a cyclotomic polynomial.

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3, 4, 5, 6, 7, 8, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 23, 24, 26, 30, 31, 32, 34, 38, 39, 40, 43, 45, 49, 54, 56, 61, 62, 63, 66, 75, 79, 80, 85, 87, 98, 101, 117, 120, 122, 127, 130, 138, 154, 161, 167, 170, 178, 183, 184, 186, 187, 191, 192, 199, 205, 207, 208 (list; graph; listen)

	OFFSET	`1,1`
	COMMENT	`While the sequence is not very interesting up to a(n)<300, there are only 4 values in the interval [400,599].`
	LINKS	`Index entries for cyclotomic polynomials, values at X`
	PROGRAM	`(PARI) for( i=1, 999, isprime( polcyclo(i, -2)) & print1( i", ")) /* for PARI < 2.4.2 use ...subst(polcyclo(i), x, -2)...*/`
	CROSSREFS	`Cf. A020501, A138920-A138940.` `Sequence in context: A051415 A037351 A077528 this_sequence A116587 A057903 A047310` `Adjacent sequences: A138925 A138926 A138927 this_sequence A138929 A138930 A138931`
	KEYWORD	`nonn`
	AUTHOR	`M. F. Hasler (www.univ-ag.fr/~mhasler), Apr 03 2008`

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Last modified December 1 13:27 EST 2009. Contains 167806 sequences.

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