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A154671
Averages of twin prime pairs k such that k*3 and k/3 are squares.
7
12, 108, 192, 432, 1452, 2028, 3468, 4800, 10092, 18252, 106032, 139968, 221952, 284592, 299568, 355008, 549552, 618348, 720300, 786432, 823728, 961068, 995328, 1009200, 1138368, 1190700, 1291008, 1529388, 1537968, 1651692, 1948908
OFFSET
1,1
LINKS
FORMULA
a(n) = 12*A154331(n)^2. - M. F. Hasler, Jan 15 2009
EXAMPLE
12*3 = 36 = 6^2, 12/3 = 4 = 2^2.
MATHEMATICA
lst={}; Do[If[PrimeQ[n-1]&&PrimeQ[n+1], s=(n*3)^(1/2); If[Floor[s]==s, AppendTo[lst, n]]], {n, 6, 10!, 6}]; lst...and/or... lst={}; Do[If[PrimeQ[n-1]&&PrimeQ[n+1], s=(n/3)^(1/2); If[Floor[s]==s, AppendTo[lst, n]]], {n, 6, 10!, 6}]; lst
Select[Mean/@Select[Partition[Prime[Range[150000]], 2, 1], #[[2]]-#[[1]] == 2&], AllTrue[{Sqrt[#/3], Sqrt[3#]}, IntegerQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Dec 06 2015 *)
PROG
(PARI) for(i=1, 999, isprime(12*i^2+1) && isprime(12*i^2-1) && print1(12*i^2", ")) \\ M. F. Hasler, Jan 15 2009
CROSSREFS
Cf. A154670.
Sequence in context: A166755 A230712 A271559 * A321672 A241230 A353047
KEYWORD
nonn
AUTHOR
STATUS
approved