OFFSET
0,5
LINKS
Amiram Eldar, Table of n, a(n) for n = 0..1667
FORMULA
a(n) = sigma(binomial(2n,n)/(n+1)) - binomial(2n,n)/(n+1), where sigma(m) is the sum of the divisors of m. - Emeric Deutsch, Dec 24 2008
EXAMPLE
a(4)=10 because the proper divisors of A000108(4)=14 are 1,2 and 7. - Emeric Deutsch, Dec 24 2008
MAPLE
with(numtheory): seq(sigma(binomial(2*n, n)/(n+1))-binomial(2*n, n)/(n+1), n = 0 .. 27); # Emeric Deutsch, Dec 24 2008
MATHEMATICA
DivisorSigma[1, #]-#&/@CatalanNumber[Range[0, 30]] (* Harvey P. Dale, Dec 05 2015 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Omar E. Pol, Dec 14 2008
EXTENSIONS
Extended by Emeric Deutsch, Dec 24 2008
STATUS
approved