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A279222
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Expansion of Product_{k>=1} 1/(1 - x^(k*(k+1)*(4*k-1)/6)).
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6
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1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 4, 5, 5, 5, 5, 5, 5, 6, 7, 7, 7, 7, 7, 7, 8, 9, 9, 9, 9, 9, 9, 10, 11, 12, 12, 12, 12, 12, 13, 15, 16, 16, 16, 16, 16, 17, 19, 20, 20, 20, 20, 20, 21, 23, 24, 25, 25, 25, 25, 26, 28, 30, 31, 31, 31, 31, 32, 34, 36, 37, 37, 37, 37, 38, 40, 42, 43, 44, 44, 44
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OFFSET
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0,8
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COMMENTS
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Number of partitions of n into nonzero hexagonal pyramidal numbers (A002412).
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LINKS
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Table of n, a(n) for n=0..90.
M. Bernstein and N. J. A. Sloane, Some canonical sequences of integers, Linear Alg. Applications, 226-228 (1995), 57-72; erratum 320 (2000), 210. [Link to arXiv version]
M. Bernstein and N. J. A. Sloane, Some canonical sequences of integers, Linear Alg. Applications, 226-228 (1995), 57-72; erratum 320 (2000), 210. [Link to Lin. Alg. Applic. version together with omitted figures]
Eric Weisstein's World of Mathematics, Hexagonal Pyramidal Number
Index to sequences related to pyramidal numbers
Index entries for related partition-counting sequences
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FORMULA
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G.f.: Product_{k>=1} 1/(1 - x^(k*(k+1)*(4*k-1)/6)).
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EXAMPLE
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a(8) = 2 because we have [7, 1] and [1, 1, 1, 1, 1, 1, 1, 1].
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MATHEMATICA
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nmax=90; CoefficientList[Series[Product[1/(1 - x^(k (k + 1) (4 k - 1)/6)), {k, 1, nmax}], {x, 0, nmax}], x]
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CROSSREFS
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Cf. A002412, A068980, A279220, A279221, A279223, A279224.
Sequence in context: A052364 A052374 A003074 * A276798 A067100 A296237
Adjacent sequences: A279219 A279220 A279221 * A279223 A279224 A279225
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KEYWORD
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nonn
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AUTHOR
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Ilya Gutkovskiy, Dec 08 2016
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STATUS
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approved
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