A242064 Smallest k such that the union of {A242033(i): 1 <= i <= k} and {A242034(i): 1 <= i <= k} includes all primes {3, ..., prime(n)}.

1, 2, 9, 9, 36, 36, 81, 220, 220, 386, 386, 386, 434, 521, 896, 896, 896, 1167, 1167, 1695, 2065, 2096, 2096, 2968, 2968, 2968, 2968, 3341, 4561, 4561, 4561, 4561, 4672, 4672, 5964, 6203, 7158, 8294, 8294, 8294, 8740, 8740, 10452, 10452, 11075, 11075, 12092

Offset

2,2

Links

Table of n, a(n) for n=2..48.

Mathematica

lpf[n_]:=lpf[n]=First[First[FactorInteger[n]]]; (*least prime factor*)
A242033=Map[lpf[#-1]&, Select[Range[6, 100000, 2], lpf[#-1]<lpf[#-3]&](*A245024*)];
A242034=Map[lpf[#-3]&, Select[Range[6, 100000, 2], lpf[#-1]>lpf[#-3]&](*A243937*)];
pos={}; NestWhile[#+1&, 2, (AppendTo[pos, Min[Position[A242033, Prime[#], 1, 1], Position[A242034, Prime[#], 1, 1]/.{}->0]]; !Last[pos]==0)&];
A242064=Rest[FoldList[Max, -Infinity, Flatten[pos]]] (* Peter J. C. Moses, Aug 14 2014 *)

Crossrefs

Cf. A242033, A242034, A242036, A242037.

Sequence in context: A198942 A168333 A238412 * A109322 A000587 A014182

Adjacent sequences: A242061 A242062 A242063 * A242065 A242066 A242067

Keyword

nonn

Author

Vladimir Shevelev, Aug 13 2014

Extensions

More terms from Peter J. C. Moses, Aug 14 2014

Status

approved