OFFSET
1,2
COMMENTS
Conjecture: a(n) exists for any n > 0.
LINKS
Zhi-Wei Sun, Table of n, a(n) for n = 1..10000
EXAMPLE
a(2) = 20 since 2 + 20 = 22 divides D(2) + D(20) = 13 + 260543813797441 = 260543813797454 = 22*11842900627157.
MATHEMATICA
d[n_]:=Sum[Binomial[n, k]Binomial[n+k, k], {k, 0, n}]
Do[m=1; Label[aa]; If[Mod[d[m]+d[n], m+n]==0, Print[n, " ", m]; Goto[bb]]; m=m+1; Goto[aa]; Label[bb]; Continue, {n, 1, 60}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Zhi-Wei Sun, Oct 02 2014
STATUS
approved