OFFSET
0,2
COMMENTS
EXAMPLE
The terms together with their prime indices begin:
1: {}
2: {1}
3: {2}
7: {4}
13: {6}
53: {16}
37: {12}
311: {64}
89: {24}
151: {36}
223: {48}
2045: {3,80}
281: {60}
3241: {4,90}
1163: {192}
827: {144}
659: {120}
9037: {4,210}
1069: {180}
17611: {5,252}
MATHEMATICA
rnnm[q_]:=Max@@Select[Range[Min@@q, Max@@q], SubsetQ[q, Range[#]]&];
posfirsts[q_]:=Table[Position[q, n][[1, 1]], {n, Min@@q, rnnm[q]}];
posfirsts[Table[Length[Union @@ Divisors/@PrimePi/@First/@If[n==1, {}, FactorInteger[n]]], {n, 1000}]]
PROG
(PARI) f(n) = my(list=List(), f=factor(n)); for (i=1, #f~, fordiv(primepi(f[i, 1]), d, listput(list, d))); #Set(list); \\ A370820
a(n) = my(k=1); while (f(k) != n, k++); k; \\ Michel Marcus, May 02 2024
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Mar 20 2024
STATUS
approved