 | ECS #8: Words |
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1. Description
Words of n letters in a four letters alphabet
2. Specification
This unlabelled structure is specified as S in
\displaystyle
\left\{ S={\rm Sequence} \left( {\rm Union} \left( a,b,c,d \right)
\right) ,a={\rm Atom},b={\rm Atom},c={\rm Atom},d={\rm Atom} \right\}
other formats
3. Coefficients
3.1. First terms
3.2. Recurrence
\displaystyle
\left\{ 4\,f \left( n \right) -f \left( n+1 \right) =0,f \left( 0
\right) =1 \right\}
other formats
3.3. Closed form
\displaystyle
{4}^{n}
other formats
3.4. Asymptotics
4. Ordinary generating function
\displaystyle
- \left( -1+4\,x \right) ^{-1}
other formats
5. References
6. Random structure
Search a combinatorial structure by: (firstTerms should be a sequence of integers, separated by commas).