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A369714
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Number of solutions to 1^4*k_1 + 2^4*k_2 + ... + n^4*k_n = 1, where k_i are from {-1,0,1}, i=1..n.
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0
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0, 1, 1, 1, 1, 1, 1, 1, 1, 2, 5, 13, 25, 56, 110, 218, 494, 1216, 2702, 6477, 14752, 35758, 83730, 208107, 499459, 1250815, 3048590, 7787399, 19260830, 49686365, 124430675, 324018684, 820906005, 2155194085, 5514650519, 14578030389, 37630395887, 100201473164
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OFFSET
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0,10
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LINKS
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FORMULA
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a(n) = [x^1] Product_{k=1..n} (x^(k^4) + 1 + 1/x^(k^4)).
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MAPLE
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b:= proc(n, i) option remember; (m-> `if`(n>m, 0, `if`(n=m, 1, b(n, i-1)+
b(abs(n-i^4), i-1)+b(n+i^4, i-1))))(i*(i+1)*(2*i+1)*(3*i^2+3*i-1)/30)
end:
a:= n-> b(1, n):
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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