In a situation when Shushan Purim falls out on Shabbat, walled cities (which can't celebrate Purim on Shabbat) read the Megillah and give Matanot Le’Evyonim on Friday, while on Sunday they have their Purim Seudah and give Mishloach Manot.
Is Tachanun omitted on that Sunday 16 Adar even though it's not really a holiday itself? Does it matter if one is in a walled city and performing specifical commands or not?