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 A338472 #21 Dec 23 2020 07:31:24
%S A338472 3,109,14519,2024592291,1536463613637,2449395996564189425,
%T A338472 4686662617019462175259,33724155827962966577589860263,
%U A338472 2606282943971359343146382147809434583605,15159042500551578738018590862773479717960671,6576976543997974825092367662248938303820921894460988333
%N A338472 (1 + Sum_{k(even)=2..p-1} 2*k^(p-1))/p as p runs through the odd primes.
%C A338472 Conjecture: (1 + Sum_{k(even)=2..p-1} 2*k^(p-1))/p is an integer iff p is an odd prime.
%t A338472 a[n_] := Module[{p = Prime[n + 1]}, (1 + 2 * Sum[k^(p - 1), {k, 2, p - 1, 2}])/p]; Array[a, 11] (* _Amiram Eldar_, Oct 29 2020 *)
%o A338472 (PARI) a(n) = my(p=prime(n+1)); (1 + sum(k=1, (p-1)\2, 2*(2*k)^(p-1)))/p; \\ _Michel Marcus_, Oct 29 2020
%Y A338472 Cf. A055030.
%K A338472 nonn
%O A338472 1,1
%A A338472 _Davide Rotondo_, Oct 29 2020