Mutations that change the nucleotide sequence without changing the amino acid sequence are

Mutations that change the nucleotide sequence without changing the amino acid sequence are synonymous mutations.

Synonymous mutations or substitution are those that change a codon with another codon that codes for the same amino acid. As a result, the synthesized amino acid sequence is not modified. Synonymous mutations usually don’t result in any phenotypic effects, so they are called silent.