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0, 21, 84, 189, 336, 525, 756, 1029, 1344, 1701, 2100, 2541, 3024, 3549, 4116, 4725, 5376, 6069, 6804, 7581, 8400, 9261, 10164, 11109, 12096, 13125, 14196, 15309, 16464, 17661, 18900, 20181, 21504, 22869, 24276, 25725, 27216, 28749
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OFFSET
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0,2
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COMMENTS
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Number of edges in a complete 7-partite graph of order 7n, K_n,n,n,n,n,n,n.
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LINKS
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FORMULA
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a(n) = t(7*n) - 7*t(n), where t(i) = i*(i+k)/2 for any k. Special case (k=1): a(n) = A000217(7*n) - 7*A000217(n). - Bruno Berselli, Aug 31 2017
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MATHEMATICA
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LinearRecurrence[{3, -3, 1}, {0, 21, 84}, 40] (* Harvey P. Dale, Jul 29 2019 *)
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PROG
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CROSSREFS
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Similar sequences are listed in A244630.
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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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