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http://www.smogon.com/dp/moves/
http://www.smogon.com/dp/moves/flatter
both links (same article) state flatter boosts special attack by one stage, it should be two
you might consider black sludge on tentacruel unless u dont mind being tricked a choice item. being tricked a scarf or specs isnt usually all bad as tentacruel can become quite dangerous.