OFFSET
1,2
COMMENTS
a(n) = #{(i,j): 1<=i<=j<=n and P(n)<=P(i)+P(j)}, P=A000041.
EXAMPLE
a(10)=14: P(10)=42 and
42<=P(10)+P(10)=42+42,42<=P(10)+P(9)=42+30, 42<=P(10)+P(8)=42+22,
42<=P(10)+P(7)=42+15, 42<=P(10)+P(6)=42+11, 42<=P(10)+P(5)=42+7,
42<=P(10)+P(4)=42+5, 42<=P(10)+P(3)=42+3, 42<=P(10)+P(2)=42+2,
42<=P(10)+P(1)=42+1, 42<=P(9)+P(9)=30+30, 42<=P(9)+P(8)=30+22,
42<=P(9)+P(7)=30+15 and 42<=P(8)+P(8)=22+22.
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Feb 06 2004
STATUS
approved