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Search: id:A078124
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| A078124 |
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Second column, M(n+1,1) for n>=0, of infinite lower triangular matrix M defined in A078122. |
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+0
17
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| 1, 3, 12, 93, 1632, 68457, 7112055, 1879090014, 1287814075131, 2325758241901161, 11213788533232011006, 145939965725683888932081, 5174322925070232320838406581, 503750821963423009552527526376232
(list; graph; listen)
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OFFSET
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0,2
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FORMULA
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The partitions of 2*3^n into powers of 3, or, the coefficient of x^(2*3^n) in 1/Product_{j=0..inf}(1-x^(3^j)) (conjecture).
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EXAMPLE
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a(1)=3 since the coefficient of x^6 in 1/Product_{j=0..inf}(1-x^(3^j)) = 1 + x + x^2 + 2x^3 + 2x^4 + 2x^5 + 3x^6 + ... is 3.
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MATHEMATICA
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m[i_, j_] := m[i, j]=If[j==0||i==j, 1, m3[i-1, j-1]]; m2[i_, j_] := m2[i, j]=Sum[m[i, k]m[k, j], {k, j, i}]; m3[i_, j_] := m3[i, j]=Sum[m[i, k]m2[k, j], {k, j, i}]; a[n_] := m[n+1, 1]
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CROSSREFS
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Cf. A078121, A078122 (matrix shift when cubed), A078123, A078125.
Sequence in context: A065087 A058337 A025503 this_sequence A115245 A145074 A162055
Adjacent sequences: A078121 A078122 A078123 this_sequence A078125 A078126 A078127
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KEYWORD
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nonn
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AUTHOR
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Paul D. Hanna (pauldhanna(AT)juno.com), Nov 18 2002
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