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A164904
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a(n) is the number of palindromic structures using a maximum of ten different symbols.
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1
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1, 1, 1, 2, 2, 5, 5, 15, 15, 52, 52, 203, 203, 877, 877, 4140, 4140, 21147, 21147, 115975, 115975, 678569, 678569, 4213530, 4213530, 27641927, 27641927, 190829797, 190829797, 1381367941, 1381367941, 10448276360, 10448276360, 82285618467
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,4
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COMMENTS
| a(n) is the number of palindromic word structures of length n using 10-ary alphabet. a(n) is the same as taking every element twice from A164864 - Number of ways of placing n labeled balls into 10 indistinguishable boxes; word structures of length n using a 10-ary alphabet.
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EXAMPLE
| Four-digit palindromes have two different digits structures: aaaa and abba. Hence a(4)=2.
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CROSSREFS
| Cf. A056470, A056471, A164864, A188164
Sequence in context: A055879 A056470 A056471 * A188164 A083849 A063501
Adjacent sequences: A164901 A164902 A164903 * A164905 A164906 A164907
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KEYWORD
| nonn
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AUTHOR
| Tanya Khovanova (tanyakh(AT)yahoo.com), Aug 30 2009
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