robjlucas

array = [{"no_in_series"=>116, "recipient_type"=>"individual", "subscriptions"=>3971},
 {"no_in_series"=>116, "recipient_type"=>"institution", "subscriptions"=>838},
 {"no_in_series"=>116, "recipient_type"=>"student", "subscriptions"=>509},
 {"no_in_series"=>115, "recipient_type"=>"individual", "subscriptions"=>3859},
 {"no_in_series"=>115, "recipient_type"=>"institution", "subscriptions"=>805},
 {"no_in_series"=>115, "recipient_type"=>"student", "subscriptions"=>441}]
 
array.group_by {|r| r["no_in_series"]}
  .map {|k,v| {k => v.map {|r| {r["recipient_type"] => r["subscriptions"]}}}}
  .map {|h| {h.keys.first => h.values.first.inject(&:merge)}}