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A211276
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a(n) = number of n-lettered words in the alphabet {1, 2, 3} with as many occurrences of the substring (consecutive subword) [1, 1] as of [1, 2].
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0
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1, 3, 7, 18, 47, 123, 328, 886, 2419, 6675, 18587, 52164, 147404, 418991, 1197002, 3434568, 9891715, 28580469, 82808899, 240511642, 700024987, 2041255981, 5962023006, 17439034426, 51075928264, 149767494573, 439619556301, 1291671623988, 3798447661874, 11179106282223, 32925086562548
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OFFSET
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0,2
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LINKS
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FORMULA
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Conjecture: n*a(n) +2*(-3*n+1)*a(n-1) +(7*n+6)*a(n-2) +2*(7*n-37)*a(n-3) +3*(-7*n+40)*a(n-4) +6*(-n-4)*a(n-5) +27*(-n+6)*a(n-6) +54*(n-6)*a(n-7)=0. - R. J. Mathar, May 31 2014
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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