MathCastle
Counting & ProbabilityMediumBinomial Theorem, Pascal & Combinatorial Identities

Binomial Theorem, Pascal & Combinatorial Identities · Medium problem

Using symmetry to rewrite (4k+1)=(43−k)\binom{4}{k+1}=\binom{4}{3-k}, evaluate ∑k=03(4k)(4k+1)\displaystyle\sum_{k=0}^{3}\binom{4}{k}\binom{4}{k+1}.