OFFSET
1,1
COMMENTS
The multiset of prime indices of a(n) is the a(n)-th row of A112798. This multiset is normal, meaning it spans an initial interval of positive integers, and periodic, meaning its multiplicities have a common divisor greater than 1.
EXAMPLE
Sequence of all normal periodic multisets begins
4: {1,1}
8: {1,1,1}
16: {1,1,1,1}
32: {1,1,1,1,1}
36: {1,1,2,2}
64: {1,1,1,1,1,1}
128: {1,1,1,1,1,1,1}
144: {1,1,1,1,2,2}
216: {1,1,1,2,2,2}
256: {1,1,1,1,1,1,1,1}
324: {1,1,2,2,2,2}
512: {1,1,1,1,1,1,1,1,1}
576: {1,1,1,1,1,1,2,2}
900: {1,1,2,2,3,3}
1024: {1,1,1,1,1,1,1,1,1,1}
MATHEMATICA
Select[Range[1000], FactorInteger[#][[-1, 1]]==Prime[Length[FactorInteger[#]]]&&GCD@@FactorInteger[#][[All, 2]]>1&]
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, May 13 2018
STATUS
approved