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A214698
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a(n) = (n^n - n^2)/2.
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1
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0, 0, 9, 120, 1550, 23310, 411747, 8388576, 193710204, 4999999950, 142655835245, 4458050224056, 151437553296042, 5556003412778910, 218946945190429575, 9223372036854775680, 413620130943168381944, 19673204037648268787550, 989209827830156794561809, 52428799999999999999999800
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OFFSET
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1,3
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LINKS
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FORMULA
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E.g.f.: (-1/2)*(lambertW(-x)/(1 + lambertW(-x)) + x*(x+1)*exp(x)). - G. C. Greubel, Jan 08 2024
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EXAMPLE
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a(3) = (27 - 9)/2 = 9.
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MAPLE
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(n^n-n^2)/2 ;
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MATHEMATICA
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PROG
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(Python)
for n in range(1, 22):
print (n**n - n*n)/2,
(Magma) [(n^n -n^2)/2: n in [1..30]]; // G. C. Greubel, Jan 08 2024
(SageMath) [(n^n -n^2)/2 for n in range(1, 31)] # G. C. Greubel, Jan 08 2024
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CROSSREFS
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Cf. A124797 is essentially equal to (n^n-n)/2.
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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