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A173036
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a(n) = binomial(n+1, 2) + 13.
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2
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13, 14, 16, 19, 23, 28, 34, 41, 49, 58, 68, 79, 91, 104, 118, 133, 149, 166, 184, 203, 223, 244, 266, 289, 313, 338, 364, 391, 419, 448, 478, 509, 541, 574, 608, 643, 679, 716, 754, 793, 833, 874, 916, 959, 1003, 1048, 1094, 1141, 1189, 1238, 1288, 1339, 1391
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OFFSET
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0,1
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COMMENTS
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LINKS
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FORMULA
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G.f.: (13 -25*x +13*x^2)/(1-x)^3.
E.g.f.: (26 +2*x +x^2)*exp(x)/2. (End)
Sum_{n>=0} 1/a(n) = 2*Pi*tanh(sqrt(103)*Pi/2)/sqrt(103). - Amiram Eldar, Dec 13 2022
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MAPLE
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MATHEMATICA
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Table[n*(n+1)/2 +13, {n, 0, 5!}]
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PROG
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(Sage) [13 + binomial(n+1, 2) for n in (0..60)] # G. C. Greubel, Feb 19 2021
(Magma) [13 + Binomial(n+1, 2): n in [0..60]]; // G. C. Greubel, Feb 19 2021
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CROSSREFS
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KEYWORD
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nonn,easy,less
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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