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A096317
a(n) is the minimal product of the smallest prime factor of each composite number in a prime gap of 2n.
1
2, 12, 120, 1680, 10080, 221760, 2217600, 34594560, 345945600, 11762150400, 29059430400, 988020633600, 21736453939200, 225268704460800, 5999261287219200, 642466345122201600, 1367831573485977600
OFFSET
1,1
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.
CROSSREFS
Cf. A096318.
Sequence in context: A326000 A245067 A052680 * A226760 A226758 A214770
KEYWORD
nonn
AUTHOR
Ray G. Opao, Aug 02 2004
STATUS
approved