A304250 Perfect powers whose prime factors span an initial interval of prime numbers.

4, 8, 16, 32, 36, 64, 128, 144, 216, 256, 324, 512, 576, 900, 1024, 1296, 1728, 2048, 2304, 2916, 3600, 4096, 5184, 5832, 7776, 8100, 8192, 9216, 11664, 13824, 14400, 16384, 20736, 22500, 26244, 27000, 32400, 32768, 36864, 44100, 46656, 57600, 65536, 72900

Offset: 1

Author

Gus Wiseman, May 13 2018

Keywords

• nonn

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.

Examples

			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}
		

Links

• Michael De Vlieger, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000837, A000961 A001597, A007916, A018783, A052409, A052410, A055932, A056239, A112798, A178472, A303431, A303709, A304450, A368682.

Programs

Mathematica

Select[Range[1000],FactorInteger[#][[-1,1]]==Prime[Length[FactorInteger[#]]]&&GCD@@FactorInteger[#][[All,2]]>1&]

Formula

Intersection of A001597 and A055932.