OFFSET
1,3
COMMENTS
a(n) = Min{A139325(n,k): 1<=k<=n}.
EXAMPLE
a(4)=Min{#{3,5,7},#{11,13},#{17,19,23},#{29,31}}=Min{3,2,3,2}=2:
..1 ...3 ...5 ...7 ... primes in first row = {3,5,7},
..9 ..11 ..13 ..15 ... primes in 2nd row = {11,13},
.17 ..19 ..21 ..23 ... primes in 3rd row = {17,19},
.25 ..27 ..29 ..31 ... primes in 4th row = {29,31}.
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Apr 14 2008
STATUS
approved