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 A090735 Number of positive squarefree numbers <=n that can be expressed as a sum of 2 squares >0. 1
 0, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 6, 6, 6, 7, 7, 7, 7, 7, 8, 8, 8, 9, 9, 9, 9, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 11, 11, 11, 11, 11, 12, 12, 12, 13, 13, 13, 13, 14, 14, 14, 14, 14, 14, 14, 14, 15, 16, 16, 16, 16, 16, 16, 16, 16, 17, 17 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,5 REFERENCES S. R. Finch, Mathematical Constants, Cambridge, 2003, p. 100 LINKS FORMULA a(n) is asymptotic to (6K/Pi^2)*n/sqrt(log(x)) where K is the Landau-Ramanujan constant PROG (PARI) a(n)=sum(i=1, n, issquarefree(i)*if(sum(u=1, i, sum(v=1, u, if(u^2+v^2-i, 0, 1))), 1, 0)) CROSSREFS Cf. A064533. Sequence in context: A114575 A131849 A244479 * A090736 A094999 A280951 Adjacent sequences:  A090732 A090733 A090734 * A090736 A090737 A090738 KEYWORD nonn AUTHOR Benoit Cloitre, Jan 18 2004 STATUS approved

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Last modified December 11 07:18 EST 2019. Contains 329914 sequences. (Running on oeis4.)