2 deleted 4 characters in body
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Retina, 5050 45 bytes

^(?>1!(1(?<=(?=\1+$)^=(1+))?(\3+$)*1$(?<!(?(1>\2?)!\3)))^(?<-1>\11+)*))*1$)

Input in unary, output 1 for abundant numbers, 0 otherwise.

There is nothing Retina-specific about this solution. The above is a pure .NET regex which matches only abundant numbers.

Try it online!Try it online! (Test suite that filters thedecimal input with the above regex.)

Retina, 50 bytes

^(?>1(?<=(?=\1+$)^(1+))?)*1$(?<!(?(1)!)(?<-1>\1)*)

Input in unary, output 1 for abundant numbers, 0 otherwise.

There is nothing Retina-specific about this solution. The above is a pure .NET regex which matches only abundant numbers.

Try it online! (Test suite that filters the input with the above regex.)

Retina, 50 45 bytes

^(?!(1(?<=(?=(?(\3+$)((?>\2?)\3)))^(1+)))*1$)

Input in unary, output 1 for abundant numbers, 0 otherwise.

There is nothing Retina-specific about this solution. The above is a pure .NET regex which matches only abundant numbers.

Try it online! (Test suite that filters decimal input with the above regex.)

1
source | link

Retina, 50 bytes

^(?>1(?<=(?=\1+$)^(1+))?)*1$(?<!(?(1)!)(?<-1>\1)*)

Input in unary, output 1 for abundant numbers, 0 otherwise.

There is nothing Retina-specific about this solution. The above is a pure .NET regex which matches only abundant numbers.

Try it online! (Test suite that filters the input with the above regex.)