id:A098235 - OEIS Search Results

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Number of ways to write n as a sum of two ordered positive squarefree numbers.

+0
3

0, 1, 2, 3, 2, 3, 4, 6, 4, 3, 4, 7, 6, 5, 6, 10, 8, 8, 6, 11, 8, 9, 8, 14, 10, 9, 10, 13, 10, 9, 10, 16, 12, 13, 12, 22, 14, 13, 14, 22, 16, 15, 18, 25, 20, 15, 16, 26, 20, 16, 14, 27, 20, 20, 14, 26, 20, 21, 18, 29, 22, 21, 22, 30, 22, 21, 22, 35, 24, 25, 22, 42, 26, 27, 26, 39 (list; graph; listen)

	OFFSET	`1,3`
	COMMENT	`a(n) ~ n * Prod[p prime, (1-2/p^2) * Prod[p^2\|n, (p^2-1)/(p^2-2)]].`
	LINKS	`T. D. Noe, Table of n, a(n) for n = 1..10000` `P. Pollack, Analytic and Combinatorial Number Theory Course Notes, p. 122, 202.`
	FORMULA	`a(1)=0 then a(n+1)=sum(k=1,n,(mu(k)mu(n+1-k))^2) - Benoit Cloitre (abmt(AT)orange.fr), Sep 24 2006` `a(n+1) = SUM(A008966(k)A008966(n-k+1): 1<=k<=n). [From Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Nov 04 2009]`
	EXAMPLE	`a(12)=7 because 12=1+11=2+10=5+7=6+6=7+5=10+2=11+1.`
	CROSSREFS	`Cf. A005117, A098236.` `Cf. A071068.` `Sequence in context: A162751 A026342 A078198 this_sequence A114868 A138239 A112484` `Adjacent sequences: A098232 A098233 A098234 this_sequence A098236 A098237 A098238`
	KEYWORD	`nonn,new`
	AUTHOR	`Ralf Stephan, Aug 31 2004`

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

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