OFFSET
1,41
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
EXAMPLE
a(29) is the first nonzero term since 29=15+14. The first nonzero even term is a(68) since 68=3(11)+5(7). Then the first even term with a value greater than one is a(86) since 86=3(7)+5(13) and 86=5(7)+3(17).
PROG
(MATLAB)
function [asubn]=ccsf(n)
% ccsf(n) returns the n-th term of the sequence of composite, coprime, square
% free sums of the integer n
r=0;
k=6;
while k<n/2,
if isprime(k)+isprime(n-k) == 0
if gcd(k, n-k) == 1
if prod(diff(factor(k)))*prod(diff(factor(n-k)))>0
r = r+1;
end
end
end
k=k+1;
end
asubn=r;
end
(PARI) a(n)=sum(k=4, (n-1)\2, gcd(k, n-k)==1&&!isprime(k)&&!isprime(n-k)&&issquarefree(k)&&issquarefree(n-k)) \\ Charles R Greathouse IV, Oct 18 2011
CROSSREFS
KEYWORD
nonn
AUTHOR
Jason Holland, Oct 16 2011
STATUS
approved