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 A309368 #5 Jul 25 2019 17:44:41 %S A309368 2,7,13,32,43,129,145,405,660,1417,2079,5999,8233,18903,37271,74912, %T A309368 131131,300239,524355,1139985,2180263,4372491,8388691,17853809, %U A309368 33715580,68704969,136183123,274127445,536871021,1100025921,2147483775,4343912079,8638792645,17309012967,34380645545 %N A309368 a(n) = Sum_{d|n} prime(n/d)^d. %F A309368 G.f.: Sum_{k>=1} prime(k)*x^k/(1 - prime(k)*x^k). %F A309368 L.g.f.: -log(Product_{k>=1} (1 - prime(k)*x^k)^(1/k)). %F A309368 a(n) ~ 2^n. %t A309368 Table[Sum[Prime[n/d]^d, {d, Divisors[n]}], {n, 1, 35}] %t A309368 nmax = 35; CoefficientList[Series[Sum[Prime[k] x^k/(1 - Prime[k] x^k), {k, 1, nmax}], {x, 0, nmax}], x] // Rest %t A309368 nmax = 35; CoefficientList[Series[-Log[Product[(1 - Prime[k] x^k)^(1/k), {k, 1, nmax}]], {x, 0, nmax}], x] Range[0, nmax] // Rest %Y A309368 Cf. A000040, A007445, A055225. %K A309368 nonn %O A309368 1,1 %A A309368 _Ilya Gutkovskiy_, Jul 25 2019