id:A113784 - OEIS Search Results

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Difference between semiprime(n) and semiprime(n+2).

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5, 4, 5, 5, 7, 7, 4, 4, 8, 8, 2, 4, 4, 8, 10, 5, 6, 6, 3, 5, 7, 7, 9, 8, 8, 8, 4, 2, 5, 6, 3, 2, 12, 16, 9, 7, 4, 3, 3, 2, 7, 10, 5, 8, 8, 2, 3, 3, 10, 12, 4, 3, 7, 8, 11, 9, 6, 7, 4, 9, 14, 8, 2, 3, 3, 4, 7, 5, 2, 3, 3, 2, 3, 7, 14, 11, 12, 12, 6, 5, 6, 8, 6, 5, 9, 11, 13, 11, 4, 6, 7, 4, 3, 3, 2, 3, 6, 9 (list; graph; listen)

	OFFSET	`1,1`
	COMMENT	`Semiprime analogue of A031131 "Difference between n-th prime and (n+2)nd prime."`
	FORMULA	`a(n) = A001358(n+2) - A001358(n).`
	EXAMPLE	`a(1) = 5 because 3rd semiprime - first semiprime = 9 - 4 = 5.` `a(2) = 4 because semiprime(4) - semiprime(2) = 10 - 6 = 4.` `a(3) = 5 because semiprime(5) - semiprime(3) = 14 - 9 = 5.` `a(4) = 5 because semiprime(6) - semiprime(4) = 15 - 10 = 5.`
	MATHEMATICA	`t = Select[ Range@320, Plus @@ Last /@ FactorInteger@# == 2 &]; Drop[t, 2] - Drop[t, -2] (* Robert G. Wilson v *)`
	CROSSREFS	`Cf. A001358, A056809.` `Adjacent sequences: A113781 A113782 A113783 this_sequence A113785 A113786 A113787` `Sequence in context: A131369 A122219 A093348 this_sequence A021651 A069214 A119807`
	KEYWORD	`easy,nonn`
	AUTHOR	`Jonathan Vos Post (jvospost2(AT)yahoo.com), Jan 20 2006`
	EXTENSIONS	`More terms from Robert G. Wilson v (rgwv(at)rgwv.com), Jan 21 2006`

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Last modified October 5 16:50 EDT 2008. Contains 144613 sequences.

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