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A078575
Sum of divisors of the average of n-th twin prime pair.
4
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
1,1
LINKS
FORMULA
a(n) = A000203(A014574(n)).
EXAMPLE
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.
MATHEMATICA
midQ[n_] := PrimeQ[n-1] && PrimeQ[n+1]; DivisorSigma[1, Select[Range[1500], midQ]] (* Amiram Eldar, Nov 03 2019 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Nov 29 2002
STATUS
approved