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