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A118259
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Numbers of strongly carefree couples (a,b) with a,b<=n.
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3
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1, 3, 7, 7, 13, 17, 27, 27, 27, 33, 47, 47, 63, 73, 85, 85, 107, 107, 131, 131, 147, 165, 195, 195, 195, 215, 215, 215, 249, 265, 303, 303, 329, 355, 385, 385, 431, 461, 495, 495, 547, 569, 625, 625, 625, 661, 721, 721, 721, 721, 763, 763, 827, 827, 877, 877
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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LINKS
| Eric Weisstein's World of Mathematics, Carefree Couple
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FORMULA
| a(n)=sum_{i,j=1...n}mu(i*j)^2 [From Benoit Cloitre (benoit7848c(AT)orange.fr), Oct 10 2009]
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PROG
| (PARI) a(n)=sum(i=1, n, sum(j=1, n, moebius(i*j)^2)) [From Benoit Cloitre (benoit7848c(AT)orange.fr), Oct 10 2009]
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CROSSREFS
| Cf. A118258, A118260.
Sequence in context: A073881 A137315 A139795 * A060845 A060215 A059478
Adjacent sequences: A118256 A118257 A118258 * A118260 A118261 A118262
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KEYWORD
| nonn
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AUTHOR
| Eric Weisstein (eric(AT)weisstein.com), Apr 20, 2006
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