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A140332
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Products of two palindromes in base 10.
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1
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0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 18, 20, 21, 22, 24, 25, 27, 28, 30, 32, 33, 35, 36, 40, 42, 44, 45, 48, 49, 54, 55, 56, 63, 64, 66, 72, 77, 80, 81, 88, 96, 99, 101, 110, 111, 112, 121, 128, 131, 132, 141, 144, 151, 154, 160, 161, 165, 171, 176, 181, 191
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OFFSET
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1,3
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COMMENTS
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Genevieve Paquin, p. 5: "Lemma 3.7: a Christoffel word can always be written as the product of two palindromes." Products of two palindromes in base 10 may be either a palindrome (i.e. 202 * 202 = 40804} or a non-palindrome (i.e. 2 * 88 = 176, or 22 * 33 = 726}. Contains A115683 as a proper subset. The nonpalindromes in this sequence are the same as the non-palindromes in A115683: {10, 12, 14, 15, 16, 18, 20, 21, 24, 25, 27, 28, 30, 32, 35, 36, 40, 42, 45, 48, 49, 54, 56, 63, 64, 72, 81, 110, 132, 154, 165, 176, 198, 220, 231, 264, 275, 297, 302, 308, 322, 330...} which is not yet a sequence in OEIS.
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LINKS
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Table of n, a(n) for n=1..67.
Genevieve Paquin, On a generalization of Christoffel words: epichristoffel words, May 27, 2008.
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FORMULA
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{i*j such that i is in A002113 and j is in A002113} = A002113 UNION A115683.
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CROSSREFS
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Cf. A002113, A115683.
Sequence in context: A033637 A084347 A051038 * A155182 A096076 A108864
Adjacent sequences: A140329 A140330 A140331 * A140333 A140334 A140335
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KEYWORD
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easy,nonn,base
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AUTHOR
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Jonathan Vos Post, May 28 2008
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STATUS
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approved
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