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 A078581 #8 Nov 03 2019 06:47:12 %S A078581 4,5,16,21,31,41,92,156,91,216,121,185,336,640,249,316,608,459,241, %T A078581 596,476,704,1296,493,627,619,1340,521,541,1072,1647,691,1416,859, %U A078581 1281,1624,1916,1445,1257,1696,4800,1301,1509,1363,1313,2804,2192,2200,1427 %N A078581 Arithmetic derivative of the average of n-th twin prime pair. %H A078581 Amiram Eldar, <a href="/A078581/b078581.txt">Table of n, a(n) for n = 1..10000</a> %F A078581 a(n) = A003415(A014574(n)). %t A078581 midQ[n_] := PrimeQ[n-1] && PrimeQ[n+1]; f[n_] := n * Total[#2 / #1 & @@@ FactorInteger[n]]; f /@ Select[Range[1500], midQ] (* _Amiram Eldar_, Nov 03 2019 *) %Y A078581 Cf. A003415, A014574, A078579. %K A078581 nonn %O A078581 1,1 %A A078581 _Reinhard Zumkeller_, Nov 29 2002