Was the answer something like these?

my @first = map { 5 * $_ + 2 } 0..3;
my @second = map { 5 * $_ + 3 } 0..3;
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You can solve that sort os thing with gcd^* of the differences between elements, and then % of any to find the additive part.

^* greatest common divisor

After Compline,
Zaxo