In order to know the explicit equation we need to know that n is the position of the number
for example n=1
3(1)+4=7
4(1)+3=7
1+7=8
2(1)+5=7
for example n=2
3(2)+4=10
4(2)+3=11
2+7=9
2(2)+5=9
we can continue proving more values but with these two we can see the only equation with both values correct in the sequence the equation is 4n+3
n=1
4(1)+3=7
n=
4(2)+3=11
n= 3
4(3)+3=15
n=4
4(4)+3=19
n=5
4(5)+3=23
n=10
4(10)+3=43