Smallest dual Sierpinski/Riesel number in base 15$15$

For integer b≥2$b\ge 2$, We define:

• Sierpinski number base b$b$: Positive integer k$k$ such that gcd(k+1,b−1)=1$gcd(k+1,b-1)=1$ and k⋅bn+1$k\cdot b^n+1$ is composite for all integer n≥1$n\ge 1$
• Riesel number base b$b$: Positive integer k$k$ such that gcd(k−1,b−1)=1$gcd(k-1,b-1)=1$ and k⋅bn−1$k\cdot b^n-1$ is composite for all integer n≥1$n\ge 1$
• Dual Sierpinski number base b$b$: Positive integer k$k$ such that gcd(k,b)=1$gcd(k,b)=1$ and gcd(k+1,b−1)=1$gcd(k+1,b-1)=1$ and bn+k$b^n+k$ is composite for all integer n≥1$n\ge 1$
• Dual Riesel number base b$b$: Positive integer k$k$ such that gcd(k,b)=1$gcd(k,b)=1$ and gcd(k−1,b−1)=1$gcd(k-1,b-1)=1$ and bn−k$b^n-k$ is composite for all integer n≥1$n\ge 1$ such that bn>k+1$b^n>k+1$

See http://www.noprimeleftbehind.net/crus/Sierp-conjectures.htm for the (conjectured) smallest Sierpinski number base b$b$, and see http://www.noprimeleftbehind.net/crus/Riesel-conjectures.htm for the (conjectured) smallest Riesel number base b$b$

If a number k$k$ is Sierpinski number base b$b$ and gcd(k,b)=1$gcd(k,b)=1$, then k$k$ is also a dual Sierpinski number base b$b$, and if a number k$k$ is Riesel number base b$b$ and gcd(k,b)=1$gcd(k,b)=1$, then k$k$ is also a dual Riesel number base b$b$, since they have the same covering set, the exception is when the prime itself is in the covering set, e.g. 11$11$ is a Riesel number base 14$14$ but not dual Riesel number base 14$14$, since its covering set is {3,5}$\{3,5\}$, but 141−11${14}^1-11$ is exactly 3$3$ and the smallest dual Riesel number base 14$14$ is 19$19$, also, 13$13$ is a Riesel number base 20$20$ but not dual Riesel number base 20$20$, since its covering set is {3,7}$\{3,7\}$, but 201−11${20}^1-11$ is exactly 7$7$ and the smallest dual Riesel number base 20$20$ is 29$29$

For b=3$b=3$, since the (conjectured) smallest Sierpinski number 125050976086$125050976086$ and the (conjectured) smallest Riesel number 63064644938$63064644938$ are coprime to 3$3$, they are also the (conjectured) smallest dual Sierpinski number and the (conjectured) smallest dual Riesel number, respectively.

For b=6$b=6$, since neither the (conjectured) smallest Sierpinski number 174308$174308$ nor the (conjectured) smallest Riesel number 84687$84687$ are coprime to 6$6$, I continue to search and found the (conjectured) smallest dual Sierpinski number 282001$282001$ and the (conjectured) smallest dual Riesel number 333845$333845$.

For b=7$b=7$, since the (conjectured) smallest Sierpinski number 1112646039348$1112646039348$ and the (conjectured) smallest Riesel number 408034255082$408034255082$ are coprime to 7$7$, they are also the (conjectured) smallest dual Sierpinski number and the (conjectured) smallest dual Riesel number, respectively.

For b=15$b=15$, neither the (conjectured) smallest Sierpinski number 91218919470156$91218919470156$ nor the (conjectured) smallest Riesel number 36370321851498$36370321851498$ are coprime to 15$15$, and they are too large to search. My question is:

What are the (conjectured) smallest dual Sierpinski number and the (conjectured) smallest dual Riesel number in base b=15$b=15$?