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A330827
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a(n) is the numbers of ways to write 2*n = u + v where the ternary representations of u and of v have the same number of digits d for d = 0..2.
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4
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1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 3, 1, 3, 1, 5, 3, 3, 5, 3, 5, 3, 3, 1, 3, 1, 1, 1, 1, 3, 1, 3, 3, 5, 3, 5, 3, 5, 5, 5, 7, 5, 7, 7, 5, 9, 7, 7, 11, 7, 9, 7, 7, 7, 11, 9, 13, 5, 9, 5, 15, 7, 9, 7, 7, 7, 7, 7, 5, 5, 5, 3, 5, 3, 5, 3, 3, 1, 3, 1, 1, 1, 1, 3, 1, 3
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OFFSET
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0,7
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COMMENTS
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In other words, a(n) is the number of ways to write 2*n as the sum of two ternary anagrams.
Leading zeros are ignored.
Two ternary anagrams have necessarily the same parity, hence an odd number cannot be the sum of two ternary anagrams.
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LINKS
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EXAMPLE
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For n = 6:
- we can write 12 as u + v in the following ways:
u v ter(u) ter(v)
- - ------ ------
5 7 12 21
6 6 20 20
7 5 21 12
- hence a(6) = 3.
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PROG
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(PARI) See Links section.
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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