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A165137
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a(n) is the number of patterns for n-character papaya words in an infinite alphabet.
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5
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1, 1, 2, 4, 10, 21, 50, 99, 250, 454, 1242, 2223, 6394, 11389, 35002
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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COMMENTS
| Papaya words are concatenations of two palindromes or palindromes themselves. A165136 is the number of papaya patterns for n-digit numbers. Thus a(n) coincides with A165136 for small n, and is greater than A165136 for larger n. The actual number of n-digit papaya numbers is A165135.
The first 19 terms of this sequence are the same as in A165136. A165137(20) = A165136(20)+10. [From Tanya Khovanova (tanyakh(AT)yahoo.com), Oct 01 2009], corrected by Franklin T. Adams-Watters, Apr 10 2011.
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LINKS
| Tanya Khovanova, Papaya Words and Numbers [From Tanya Khovanova (tanyakh(AT)yahoo.com), Oct 01 2009]
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EXAMPLE
| There are two types of two-digit papaya numbers: aa, or ab. Hence a(2) = 2. There are four types of three-digit papaya numbers: aaa, aab, aba, abb. Hence a(3) = 4.
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CROSSREFS
| Cf. A165136, A165135, A165610, A165611, A188792.
Sequence in context: A018003 A204804 A165136 * A065023 A123445 A104431
Adjacent sequences: A165134 A165135 A165136 * A165138 A165139 A165140
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KEYWORD
| more,nonn
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AUTHOR
| Sergei Bernstein and Tanya Khovanova (tanyakh(AT)yahoo.com), Sep 04 2009
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EXTENSIONS
| a(0) and a(7)-a(14) from Franklin T. Adams-Watters (FrankTAW(AT)Netscape.net), Apr 10 2011
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