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A118230
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Column 3 of triangle A118229, starting with row 1 to include leading zeros.
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1
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0, 0, 1, -1, 0, 0, -1, 2, 0, -1, 1, -1, -2, 1, 1, 0, 2, -2, -1, 0, 0, 1, 1, -1, -4, 2, 1, 1, 0, 0, 1, 0, 2, -6, 3, 0, -6, 7, 1, -2, 8, -8, -5, -5, -2, 12, 3, -7, -6, -9, 1, 18, 6, -21, -9, -5, 4, 25, -1, 1, 2, -39, -1, 35, 0, 3, 3, -18, -22, 37, 5, -5, 8, -48, 9, 45, -10, -4, 5, -55, 10, 40, -17, -35, 4, -2, -11, 61, 4, -13
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,8
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FORMULA
| Sum_{k=1..n, gcd(n,k)=1} a(k) = 1 when n=4, 0 elsewhere.
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PROG
| (PARI) {a(n)=(matrix(n+2, n+2, r, c, if(r>=c, if(gcd(r-c+1, c)==1, 1, 0)))^-1)[n, 3]}
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CROSSREFS
| Cf. A118229.
Sequence in context: A099494 A030341 A121444 * A179181 A153246 A025889
Adjacent sequences: A118227 A118228 A118229 * A118231 A118232 A118233
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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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