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Search: id:A087991
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| A087991 |
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Number of non-palindromic divisors of n. |
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+0
4
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| 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 0, 1, 2, 1, 2, 1, 2, 1, 3, 1, 2, 0, 2, 1, 3, 1, 2, 2, 3, 1, 3, 1, 0, 2, 2, 1, 4, 1, 3, 2, 3, 1, 3, 0, 3, 2, 2, 1, 6, 1, 2, 2, 3, 2, 0, 1, 3, 2, 4, 1, 5, 1, 2, 3, 3, 0, 4, 1, 5, 2, 2, 1, 6, 2, 2, 2, 0, 1, 6, 2, 3, 2, 2, 2, 6, 1, 3, 0, 5, 0, 4, 1, 4, 4
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OFFSET
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1,20
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FORMULA
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a(n)=A000005[n]-A087990[n].
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EXAMPLE
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n=132: divisors={1,2,3,4,6,11,12,22,33,44,66,132},
revdivisors={1,2,3,4,6,11,21,22,33,44,66,231}, a[132]=2;
so two of 12 divisors of n are non-palindromic:{21,132}.
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CROSSREFS
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Cf. A087990, A062687.
Sequence in context: A029376 A029359 A038698 this_sequence A144095 A076092 A080468
Adjacent sequences: A087988 A087989 A087990 this_sequence A087992 A087993 A087994
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), Oct 08 2003
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