A078575 Sum of divisors of the average of n-th twin prime pair.

7, 12, 28, 39, 72, 96, 168, 195, 216, 280, 288, 372, 546, 508, 468, 560, 744, 720, 576, 840, 840, 1344, 1240, 1152, 1170, 1440, 1860, 1248, 1296, 2016, 2178, 1656, 2184, 2016, 2223, 3024, 2640, 2976, 2340, 3136, 3315, 3024, 2808, 3168, 3072, 4320, 4032

Offset: 1

Author

Reinhard Zumkeller, Nov 29 2002

Keywords

• nonn

Examples

			4th twin prime pair = (A001359(4), A006512(4)) = (17,19), hence A014574(4) = 18 with divisors = {1,2,3,6,9,18} therefore a(4) = 1+2+3+6+9+18 = 39.
		

Links

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

Crossrefs

Cf. A000203, A014574, A078574, A078576, A078577.

Programs

Mathematica

midQ[n_] := PrimeQ[n-1] && PrimeQ[n+1]; DivisorSigma[1, Select[Range[1500], midQ]] (* Amiram Eldar, Nov 03 2019 *)

Formula

a(n) = A000203(A014574(n)).