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Search: id:A159886
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| A159886 |
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Values k such that A000203(x)= k has more than one solution. |
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+0
2
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| 12, 18, 24, 31, 32, 42, 48, 54, 56, 60, 72, 80, 84, 90, 96, 98, 104, 108, 114, 120, 124, 126, 128, 132, 140, 144, 152, 156, 168, 180, 182, 186, 192, 210, 216, 224, 228, 234, 240, 248, 252, 264, 270, 272, 280, 288, 294, 308, 312, 320, 324, 336, 342, 360, 372, 378, 384, 390
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Numbers k with A054973(k) >= 2. Numbers k which occur in A000203 more than once.
Numbers k = A007609(n) with A007609(n+1) - A007609(n) = 0.
Does this sequence have finite density? [From Franklin T. Adams-Watters (FrankTAW(AT)Netscape.net), Jun 18 2009]
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LINKS
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Franklin T. Adams-Watters, Table of n, a(n) fora(n) <= 10000: n=1,...,1095.
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EXAMPLE
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a(1)=12 as the multiplicity of the value 12 is 2: 12 = sigma(6) = sigma(11).
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PROGRAM
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Contribution from Franklin T. Adams-Watters (FrankTAW(AT)Netscape.net), Jun 18 2009: (Start)
(PARI) na(n) = local(v, s); v=vector(n); for(k=1, n, s=sigma(k); if(s<=n, v[s]++)); v
la(n) = local(v, r); v=na(n); r=[]; for(k=1, n, if(v[k]>1, r=concat(r, [k]))); r (End)
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CROSSREFS
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Cf. A000203, A054973, A007609, A007368.
Sequence in context: A136446 A074726 A091013 this_sequence A113756 A055482 A076485
Adjacent sequences: A159883 A159884 A159885 this_sequence A159887 A159888 A159889
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KEYWORD
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nonn
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AUTHOR
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Jaroslav Krizek (jaroslav.krizek(AT)atlas.cz), Apr 25 2009
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EXTENSIONS
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Edited and extended by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 28 2009
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