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A011907
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[ n(n-1)(n-2)/25 ].
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0
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0, 0, 0, 0, 0, 2, 4, 8, 13, 20, 28, 39, 52, 68, 87, 109, 134, 163, 195, 232, 273, 319, 369, 425, 485, 552, 624, 702, 786, 876, 974, 1078, 1190, 1309, 1436, 1570, 1713, 1864, 2024, 2193, 2371, 2558, 2755, 2961
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,6
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FORMULA
| a(n) = +3*a(n-1) -3*a(n-2) +a(n-3) +a(n-25) -3*a(n-26) +3*a(n-27) -a(n-28). G.f.: x^5*(2-2*x+2*x^2-x^3+x^4-x^5+2*x^6-x^7+x^8+x^12-x^13+2*x^14-x^15+x^16-x^17+2*x^18-2*x^19+3*x^20-2*x^21+x^22) / ( (-1+x)^4*(1+x^4+x^3+x^2+x)*(x^20+x^15+x^10+x^5+1) ). [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 15 2010]
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CROSSREFS
| Sequence in context: A186752 A030503 A084684 * A056133 A172131 A173721
Adjacent sequences: A011904 A011905 A011906 * A011908 A011909 A011910
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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