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->n{s=("*+"*n).chars.reduce(-~n*n/2;n.times2){|i|s=s.digits.inject|x,y|eval ("*+"*n)[i]x.digits*y};s}
Try it online!Try it online!
->n{s=-~n*n/2;n.times{|i|s=s.digits.inject ("*+"*n)[i]};s}
Try it online!
->n{("*+"*n).chars.reduce(-~n*n/2){|x,y|eval x.digits*y}}
