OFFSET
1,1
COMMENTS
A prime index of n is a number m such that prime(m) divides n. The multiset of prime indices of n is row n of A112798.
EXAMPLE
The terms together with their prime indices begin:
3: {2} 67: {19} 158: {1,22}
5: {3} 69: {2,9} 179: {41}
11: {5} 77: {4,5} 191: {43}
17: {7} 83: {23} 202: {1,26}
26: {1,6} 86: {1,14} 206: {1,27}
31: {11} 87: {2,10} 211: {47}
35: {3,4} 94: {1,15} 217: {4,11}
38: {1,8} 109: {29} 235: {3,15}
39: {2,6} 119: {4,7} 237: {2,22}
41: {13} 127: {31} 241: {53}
49: {4,4} 129: {2,14} 244: {1,1,18}
57: {2,8} 133: {4,8} 253: {5,9}
58: {1,10} 146: {1,21} 274: {1,33}
59: {17} 148: {1,1,12} 277: {59}
65: {3,6} 157: {37} 278: {1,34}
MATHEMATICA
Select[Range[100], Length[Divisors[#]] == Length[Union@@Divisors/@PrimePi/@First/@If[#==1, {}, FactorInteger[#]]]&]
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Mar 14 2024
STATUS
approved