A078581 Arithmetic derivative of the average of n-th twin prime pair.

4, 5, 16, 21, 31, 41, 92, 156, 91, 216, 121, 185, 336, 640, 249, 316, 608, 459, 241, 596, 476, 704, 1296, 493, 627, 619, 1340, 521, 541, 1072, 1647, 691, 1416, 859, 1281, 1624, 1916, 1445, 1257, 1696, 4800, 1301, 1509, 1363, 1313, 2804, 2192, 2200, 1427

Offset: 1

Author

Reinhard Zumkeller, Nov 29 2002

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A003415, A014574, A078579.

Programs

Mathematica

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 *)

Formula

a(n) = A003415(A014574(n)).