
EXAMPLE

a(5) = 10080: 2*5 = 10. The first occurrence of a prime gap of 10 comes after 139, with the composite numbers 140,141,142,143,144,145,146,147,148 whose smallest prime factors are 2,3,2,11,2,5,2,3,2, respectively. However, their product is 15840, which is not minimal. The 6th occurrence of a prime gap of 10 comes after 409, with the composite numbers 410,411,412,413,414,415,416,417,418 having the smallest prime factors 2,3,2,7,2,5,2,3,2 respectively. Their product is 10080, which is minimal.
