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A078576 Sum of distinct prime factors of the average of n-th twin prime pair. 3
2, 5, 5, 5, 10, 12, 10, 5, 22, 5, 28, 10, 10, 5, 16, 24, 10, 10, 52, 18, 34, 17, 5, 23, 34, 29, 10, 108, 112, 21, 10, 142, 28, 29, 12, 27, 48, 17, 64, 25, 5, 51, 76, 53, 43, 21, 29, 16, 37, 36, 72, 10, 144, 288, 53, 154, 18, 318, 35, 23, 42, 18, 352, 34, 16, 81, 29, 378, 12 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
FORMULA
a(n) = A008472(A014574(n)).
EXAMPLE
12th twin prime pair = (A001359(12), A006512(12)) = (149,151), hence A014574(12) = 150 = 2*3*5*5, therefore a(12) = 2+3+5 = 10.
MATHEMATICA
midQ[n_] := PrimeQ[n-1] && PrimeQ[n+1]; f[n_] := Plus @@ FactorInteger[n][[;; , 1]]; f /@ Select[Range[3000], midQ] (* Amiram Eldar, Nov 03 2019 *)
CROSSREFS
Sequence in context: A171438 A200683 A286541 * A256302 A205396 A082086
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Nov 29 2002
STATUS
approved

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Last modified April 13 12:28 EDT 2024. Contains 371641 sequences. (Running on oeis4.)