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 A086455 #17 May 07 2025 08:25:09
%S A086455 1,3,4,7,6,8,15,13,12,14,31,18,20,24,31,40,30,32,63,38,42,44,48,57,54,
%T A086455 60,62,127,68,72,74,80,121,84,90,98,102,104,108,110,114,133,156,128,
%U A086455 255,132,138,140,150,152,158,164,168,183,174,180,182,192,194,198
%N A086455 Sum of divisors of prime powers: sigma(p^e).
%H A086455 R. J. Mathar, <a href="/A086455/b086455.txt">Table of n, a(n) for n = 1..10000</a>
%H A086455 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/DivisorFunction.html">Divisor Function</a>.
%H A086455 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PrimePower.html">Prime Power</a>.
%F A086455 a(n) = A000203(A000961(n)).
%F A086455 a(n) = (p^(e+1)-1)/(p-1), where p^e = A000961(n).
%F A086455 a(n) = (A025473(n)^(A025474(n)+1)-1)/(A025473(n)-1).
%p A086455 A086455 := proc(n)
%p A086455 numtheory[sigma](A000961(n)) ;
%p A086455 end proc: # _R. J. Mathar_, Jun 04 2016
%t A086455 DivisorSigma[1, #]& /@ Join[{1}, Select[Range[2, 200], PrimePowerQ]] (* _Jean-François Alcover_, Feb 10 2018 *)
%o A086455 (PARI) list(lim) = apply(sigma, select(x -> x == 1 || isprimepower(x), vector(lim, i, i))); \\ _Amiram Eldar_, May 07 2025
%Y A086455 Cf. A000203, A000961, A025473, A025474, A086454.
%K A086455 nonn
%O A086455 1,2
%A A086455 _Reinhard Zumkeller_, Jul 20 2003