OFFSET
2,5
COMMENTS
Zeros indicate prime indices.
EXAMPLE
a(15) gives (15 + 3) / 2 = 9, (9 + 3) / 2 = 6, (6 + 2) / 2 = 4, (4 + 2) / 2 = 3. Four iterations were required to reach a prime, so a(15) = 4.
MATHEMATICA
f[n_] := Length@ NestWhileList[(# + FactorInteger[#][[1, 1]])/2 &, n, ! PrimeQ@ # &] - 1; Array[f, 105, 2]
CROSSREFS
KEYWORD
nonn
AUTHOR
Grant Garcia, Jan 12 2011
STATUS
approved