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A056119
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a(n) = n*(n+13)/2.
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13
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0, 7, 15, 24, 34, 45, 57, 70, 84, 99, 115, 132, 150, 169, 189, 210, 232, 255, 279, 304, 330, 357, 385, 414, 444, 475, 507, 540, 574, 609, 645, 682, 720, 759, 799, 840, 882, 925, 969, 1014, 1060, 1107, 1155, 1204, 1254, 1305, 1357, 1410, 1464, 1519, 1575
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OFFSET
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0,2
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LINKS
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FORMULA
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G.f.: x*(7-6*x)/(1-x)^3.
If we define f(n,i,a) = Sum_{k=0..n-i} binomial(n,k)*Stirling1(n-k,i)*Product_{j=0..k-1} (-a-j), then a(n) = -f(n,n-1,7), for n >= 1. - Milan Janjic, Dec 20 2008
Sum_{n>=1} (-1)^(n+1)/a(n) = 4*log(2)/13 - 263111/2342340. - Amiram Eldar, Jan 10 2021
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PROG
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(Magma) [n*(n+13)/2: n in [0..50]]; // G. C. Greubel, Jan 18 2020
(Sage) [n*(n+13)/2 for n in (0..50)] # G. C. Greubel, Jan 18 2020
(GAP) List([0..50], n-> n*(n+13)/2 ); # G. C. Greubel, Jan 18 2020
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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