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A341043
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a(n) = 16*n^3 - 36*n^2 + 30*n - 9.
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0
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1, 35, 189, 559, 1241, 2331, 3925, 6119, 9009, 12691, 17261, 22815, 29449, 37259, 46341, 56791, 68705, 82179, 97309, 114191, 132921, 153595, 176309, 201159, 228241, 257651, 289485, 323839, 360809, 400491, 442981, 488375, 536769
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OFFSET
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1,2
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COMMENTS
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The n-th term of A155883 (hexagonal bifrustum numbers) has a hexagonal pyramid of [n - 1] set on each of its two hexagonal faces.
The digital roots run recursively 1, 8, 9.
The sum of the first n consecutive terms is the square of the n-th hexagonal number.
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LINKS
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FORMULA
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a(n) = 16*n^3 - 36*n^2 + 30*n - 9.
G.f.: x*(1 + 31*x + 55*x^2 + 9*x^3)/(1 - x)^4. - Stefano Spezia, Feb 04 2021
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EXAMPLE
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For n = 3 the solution is 173 + 8 + 8 = 189.
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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_David Z. Crookes_, Feb 03 2021
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STATUS
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approved
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