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Search: id:A143458
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| A143458 |
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Expansion of 1/(x^k*(1-x-3*x^(k+1))) for k=7. |
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+0
2
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| 1, 4, 7, 10, 13, 16, 19, 22, 25, 37, 58, 88, 127, 175, 232, 298, 373, 484, 658, 922, 1303, 1828, 2524, 3418, 4537, 5989, 7963, 10729, 14638, 20122, 27694, 37948, 51559, 69526, 93415, 125602, 169516, 229882, 312964, 426808, 581485, 790063, 1070308
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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a(n) is also the number of length n quaternary words with at least 7 0-digits between any other digits.
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FORMULA
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G.f.: 1/(x^7*(1-x-3*x^8)).
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MAPLE
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a := proc(k::nonnegint) local n, i, j; if k=0 then unapply (4^n, n) else unapply ((Matrix(k+1, (i, j)-> if (i=j-1) or j=1 and i=1 then 1 elif j=1 and i=k+1 then 3 else 0 fi)^(n+k))[1, 1], n) fi end(7): seq (a(n), n=0..57);
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CROSSREFS
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7th column of A143461.
Sequence in context: A016777 A143460 A143459 this_sequence A004084 A121381 A143457
Adjacent sequences: A143455 A143456 A143457 this_sequence A143459 A143460 A143461
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KEYWORD
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nonn
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AUTHOR
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Alois P. Heinz (heinz(AT)hs-heilbronn.de), Aug 16 2008
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