I don't know any string of length 7 contains less than 7 distinct palindrome substrings. Anyone can put the answer for 7, pls?

It may be too later.
for n = 7
1 : NO
2 : NO
3 : NO
4 : NO
5 : NO
6 : NO
7 : aaaaaaa
for n = 15
1 : NO
2 : NO
3 : NO
4 : NO
5 : NO
6 : NO
7 : NO
8 : aababbaababbaab
9 : aaababbaaababba
10 : aaaababbaaaabab
11 : aaaaababbaaaaab
12 : aaaaaaababbaaaa
13 : aaaaaaaababbaaa
14 : aaaaaaaaababbaa
15 : aaaaaaaaaababba