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Search: id:A084902
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| 0, 1, 15, 150, 1250, 9375, 65625, 437500, 2812500, 17578125, 107421875, 644531250, 3808593750, 22216796875, 128173828125, 732421875000, 4150390625000, 23345947265625, 130462646484375, 724792480468750, 4005432128906250
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OFFSET
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0,3
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COMMENT
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Binomial transform of A084901. Fourth binomial transform of heptagonal numbers A000566. Fifth binomial transform of (0,1,5,0,0,0,....).
Number of n-permutations of 6 objects u, v, w, z, x, y with repetition allowed, containing exactly two u's. Example: a(2)=15 because we have : uuw, uuv, uuz, uux, uuy, uwu, uvu, uzu, uxu, uyu, wuu, vuu, zuu, xuu, yuu - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Dec 30 2007
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FORMULA
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G.f.: x/(1 - 5x)^3
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MAPLE
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seq(seq(binomial(i+1, j)*5^(i-1), j =i-1), i=0..20); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Dec 30 2007
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CROSSREFS
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Cf. A038243.
Sequence in context: A022739 A085375 A081135 this_sequence A021364 A016103 A041424
Adjacent sequences: A084899 A084900 A084901 this_sequence A084903 A084904 A084905
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KEYWORD
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easy,nonn
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AUTHOR
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Paul Barry (pbarry(AT)wit.ie), Jun 10 2003
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