OFFSET
1,1
FORMULA
a(n) = A289280(a(n-1)) + 1 for n > 1.
EXAMPLE
a(2) = 5 since the least k > a(1) such that rad(k) | a(1) is 4, and 4 + 1 = 5.
a(3) = 26 since the least k > a(2) such that rad(k) | a(2) is 25, and 25 + 1 = 26.
a(4) = 33 since the smallest k > 26 such that rad(k) | 26 is 32, and 32 + 1 = 33, etc.
MATHEMATICA
rad[x_] := rad[x] = Times @@ FactorInteger[x][[All, 1]];
NestList[(k = # + 1; While[! Divisible[#, rad[k]], k++]; k + 1) &, 2, 20]
CROSSREFS
KEYWORD
nonn,hard
AUTHOR
Michael De Vlieger, Nov 15 2023
STATUS
approved