Chabad says that
We find a range of opinions concerning how often the mitzvah of remembering Amalek...
My rabbi (an Aish graduate) told me that wiping out Amalek's name is the mitzvah. Which is true?
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R Eliezer Melamed (Peninei Halakha here) answers as follows
Three mitzvot in the Torah relate to Amalek.
The first is a positive commandment to remember what Amalek did to us, as the Torah says: “Remember what Amalek did to you on your journey, as you left Egypt” (Devarim 25:17).
The second is a negative commandment not to forget what Amalek did to us, as the Torah says: “Do not forget” (ibid. 19).
The third is a positive commandment to eradicate Amalek’s offspring from the world, as the Torah says: “Therefore, when the Lord your God grants you safety from all your enemies around you, in the land that the Lord your God is giving you as a hereditary portion, you shall blot out the memory of Amalek from under heaven” (ibid.).
See also mitzvot #188/#189 of the 248 positive mitzvot and #59 of the 365 negative mitzvot in the Rambam’s Sefer HaMitzvot and #76/#77 of the 77 positive mitzvot that can be observed today as listed in the Chofetz Chaim’s Sefer HaMitzvot HaKatzar as well as #194 of the negative.