id:A143202 - OEIS Search Results

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Numbers having exactly two distinct prime factors p, q with q=p+2.

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15, 35, 45, 75, 135, 143, 175, 225, 245, 323, 375, 405, 675, 875, 899, 1125, 1215, 1225, 1573, 1715, 1763, 1859, 1875, 2025, 3375, 3599, 3645, 4375, 5183, 5491, 5625, 6075, 6125, 6137, 8575, 9375, 10125, 10403, 10935, 11663, 12005, 16875, 17303, 18225 (list; graph; listen)

	OFFSET	`1,1`
	COMMENT	`A143201(a(n)) = 3.` `A020639(a(n)) in A001359 and A006530(a(n)) in A006512;` `A001221(a(n))=2;` `subsequence of A007774; A037074 is a subsequence.`
	LINKS	`Eric Weisstein's World of Mathematics, Twin Primes` `Index entries for primes, gaps between`
	EXAMPLE	`a(1) = 15 = 3 * 5 = A001359(1) * A006512(1);` `a(2) = 35 = 5 * 7 = A001359(2) * A006512(2);` `a(3) = 45 = 3^2 * 5 = A001359(1)^2 * A006512(1);` `a(4) = 75 = 3 * 5^2 = A001359(1) * A006512(1)^2;` `a(5) = 135 = 3^3 * 5 = A001359(1)^3 * A006512(1);` `a(6) = 143 = 11 * 13 = A001359(3) * A006512(3);` `a(7) = 175 = 5^2 * 7 = A001359(2)^2 * A006512(2);` `a(8) = 225 = 3^2 * 5^2 = A001359(1)^2 * A006512(1)^2;` `a(9) = 245 = 5 * 7^2 =A001359(2) * A006512(2)^2;` `a(10) = 323 = 17 * 19 = A001359(4) * A006512(4);` `a(11) = 375 = 3 * 5^3 = A001359(1) * A006512(1)^3;` `a(12) = 405 = 3^4 * 5 = A001359(1)^4 * A006512(1).`
	CROSSREFS	`Sequence in context: A146319 A114988 A130871 this_sequence A108668 A162280 A063532` `Adjacent sequences: A143199 A143200 A143201 this_sequence A143203 A143204 A143205`
	KEYWORD	`nonn`
	AUTHOR	`Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Aug 12 2008`

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Last modified December 8 08:31 EST 2009. Contains 170430 sequences.

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