This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A239310 #47 Apr 04 2016 10:33:32 %S A239310 6,9,12,15,18,20,21,24,27,30,33,36,39,40,42,45,48,50,51,54,57,60,63, %T A239310 66,69,70,72,75,78,80,81,84,87,90,93,96,99,100,102,105,108,110,111, %U A239310 114,117,120,123,126,129,130,132,135,138,140,141,144,147 %N A239310 Numbers of the form A001700(n)*k, n>=1, k>=2. %C A239310 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). %F A239310 a(n) ~ kn, where k = 2.441823902640895564.... (This constant exists since A001700 grows exponentially.) - _Charles R Greathouse IV_, Apr 04 2016 %e A239310 a(n)=50 appears because A001700(2)=10, so T(6,3)=50 in (1,4)- and (2,3)-Pascal triangles. %o A239310 (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 %Y A239310 Cf. A001700. %Y A239310 Cf. A007318 (Pascal's triangle), A029600 ((2,3)-Pascal triangle), A095666 ((1,4)-Pascal triangle). %K A239310 nonn,easy %O A239310 1,1 %A A239310 _Bob Selcoe_, Mar 31 2016