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A118232
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Column 1 of triangle A118231.
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0
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1, -2, -2, 4, -2, 2, 4, -6, -4, 6, -4, 4, 14, -14, -8, 8, -16, 18, 8, -12, 6, -6, -6, -10, 28, -6, -10, 4, -2, 4, -8, -2, -18, 48, -20, 0, 54, -70, -18, 32, -76, 86, 62, 14, 14, -110, -40, 124, 62, 94, -24, -224, -66, 224, 134, 62, -72, -286, 14, 8, -14, 474, 10, -458
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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PROG
| (PARI) {a(n)=(matrix(n, n, r, c, if(r>=c, if(gcd(r-c+1, c)==1, 1, 0)))^-2)[n, 1]}
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CROSSREFS
| Cf. A118231.
Sequence in context: A143230 A072301 A127171 * A115070 A064145 A175462
Adjacent sequences: A118229 A118230 A118231 * A118233 A118234 A118235
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KEYWORD
| sign
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AUTHOR
| Leroy Quet, Paul D. Hanna (pauldhanna(AT)juno.com), Apr 16 2006
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