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 A098426 #7 Mar 02 2025 07:57:31 %S A098426 1,2,4,6,16,27,64,66,94,287,1024,645,2380,6723,12094,7136,36772,38733, %T A098426 161254,241083,571714,1203173,4194304,2005009,2162496,8739877,6699838, %U A098426 27330423,112844656,41322885,252807388,201501336,419398108,2840231975 %N A098426 a(n)=(1/2)*sum(i=0,n,rad(binomial(n,i))) where rad(k)=A007947(k). %C A098426 For n>1 a(n) odd seems to imply 2*phi(n)<n where phi= totient function. %Y A098426 Halved row sums of A080396. %K A098426 nonn %O A098426 1,2 %A A098426 _Benoit Cloitre_, Oct 26 2004