1,13

a(n)<=A100950(n)<=A100949(n)<=Min{A000720(n), A072000(n)}.

a(n) = A000040(i) + A006881(j) for some i and j, such that A000040(i) is not a factor of A006881(j);

a(A100952(n)) = 0.

a(A160373(n)) = n and a(m) <> n for m < A160373(n). [From Reinhard Zumkeller, May 11 2009]

R. Zumkeller, Table of n, a(n) for n = 1..10000

A100949(21) = #{7+2*7, 11+2*5, 17+2*2} = 3,

a(21) = #{11+2*5} = 1.

Sequence in context: A113277 A114855 A221381 * A190608 A011991 A234931

Adjacent sequences: A100948 A100949 A100950 * A100952 A100953 A100954

nonn

Reinhard Zumkeller, Nov 23 2004

approved