 | ECS #1073: A simple regular expression |
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1. Description
No description available
2. Specification
This unlabelled structure is specified as S in
\displaystyle
\left\{ S={\rm Prod} \left( {\rm Union} \left( {\rm Sequence} \left( {
\rm Prod} \left( Z,Z \right) \right) ,{\rm Sequence} \left( Z \right)
\right) ,{\rm Union} \left( Z,Z \right) \right) \right\}
other formats
3. Coefficients
3.1. First terms
3.2. Recurrence
\displaystyle
\left\{ -f \left( n \right) -f \left( n+1 \right) +6=0,f \left( 0
\right) =0,f \left( 1 \right) =4,f \left( 2 \right) =2 \right\}
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3.3. Closed form
\displaystyle
3- \left( -1 \right) ^{-n}+\cases{-2&$n=0$\cr 0&otherwise\cr}
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3.4. Asymptotics
4. Ordinary generating function
\displaystyle
-2\,{\frac {x \left( x+2 \right) }{ \left( -1+x \right) \left( x+1
\right) }}
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5. References
6. Random structure
Search a combinatorial structure by: (firstTerms should be a sequence of integers, separated by commas).