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.
LINKS
Robert Israel, Table of n, a(n) for n = 1..1567
EXAMPLE
The sequence of terms together with their prime indices begins:
2: {1}
3: {2}
5: {3}
11: {5}
15: {2,3}
31: {11}
33: {2,5}
47: {15}
55: {3,5}
93: {2,11}
127: {31}
137: {33}
141: {2,15}
155: {3,11}
165: {2,3,5}
211: {47}
235: {3,15}
257: {55}
341: {5,11}
381: {2,31}
MAPLE
S:= {2}: count:= 1:
for n from 3 by 2 while count < 100 do
F:= ifactors(n)[2];
if max(map(t -> t[2], F))=1 and {seq(numtheory:-pi(t[1]), t=F)} subset S then
S:= S union {n}; count:= count+1;
fi
od:
sort(convert(S, list)); # Robert Israel, Mar 22 2019
MATHEMATICA
aQ[n_]:=Switch[n, 1, False, 2, True, _?(!SquareFreeQ[#]&), False, _, And@@Cases[FactorInteger[n], {p_, k_}:>aQ[PrimePi[p]]]];
Select[Range[1000], aQ]
CROSSREFS
Contains A007097 except for 1.
KEYWORD
nonn
AUTHOR
Gus Wiseman, Mar 18 2019
STATUS
approved