OFFSET

1,1

COMMENTS

The sequence has prime factorization (13*197)^12, (13*1093)^12, (13*1733)^12, (13*17*139)^12, (13*7877)^12, (13*16069)^12.

FORMULA

a(n) = is the n-th number rf such that both rf and rf-1 are refactorable and 13 is the smallest prime divisor of rf.

EXAMPLE

a(1)=(13*197)^12 is the first number rf such that rf refactorable, 13 is the smallest prime of rf and rf-1 is refactorable.

CROSSREFS

KEYWORD

nonn,bref

AUTHOR

Walter Kehowski, Jun 22 2006

STATUS

approved