OFFSET
1,1
COMMENTS
Numbers that are central coefficients T(2k,k) k>=2 in (a,b)-Pascal triangles, where (a,b) represent boundary conditions; i.e., T(2k,k) = (a+b)*A001700(k-1).
FORMULA
a(n) ~ kn, where k = 2.441823902640895564.... (This constant exists since A001700 grows exponentially.) - Charles R Greathouse IV, Apr 04 2016
EXAMPLE
a(n)=50 appears because A001700(2)=10, so T(6,3)=50 in (1,4)- and (2,3)-Pascal triangles.
PROG
(PARI) is(n)=my(k=1, t=3); while(n>=2*t, if(n%t==0, return(1)); k++; t=binomial(2*k+1, k+1)); 0 \\ Charles R Greathouse IV, Apr 04 2016
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Bob Selcoe, Mar 31 2016
STATUS
approved