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A018212
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Alkane (or paraffin) numbers l(11,n).
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1
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1, 5, 25, 85, 255, 651, 1519, 3235, 6470, 12190, 21942, 37854, 63090, 101850, 160050, 245322, 367983, 541035, 781495, 1110395, 1554553, 2146573, 2927145, 3945045, 5260060, 6942988, 9079292, 11769100, 15131700, 19305540
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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REFERENCES
| S. M. Losanitsch, Die Isomerie-Arten bei den Homologen der Paraffin-Reihe, Chem. Ber. 30 (1897), 1917-1926.
Winston C. Yang (paper in preparation).
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LINKS
| N. J. A. Sloane, Classic Sequences
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FORMULA
| G.f.: (1+6*x^2+x^4)/((1-x)^5*(1-x^2)^4) [ N. J. A. Sloane (njas(AT)research.att.com) ]
l(c, r) = 1/2 binomial(c+r-3, r) + 1/2 d(c, r), where d(c, r) is binomial((c + r - 3)/2, r/2) if c is odd and r is even, 0 if c is even and r is odd, binomial((c + r - 4)/2, r/2) if c is even and r is even, binomial((c + r - 4)/2, (r - 1)/2) if c is odd and r is odd.
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CROSSREFS
| Sequence in context: A147122 A051229 A058919 * A181477 A147274 A147034
Adjacent sequences: A018209 A018210 A018211 * A018213 A018214 A018215
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Winston C. Yang (yang(AT)math.wisc.edu)
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