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A154675
Averages of twin prime pairs k such that k*13 and k/13 are squares.
4
1872, 7488, 11700, 825552, 990288, 1123668, 1629108, 3146832, 3302208, 4680000, 6627348, 7667712, 8783892, 15502032, 16017300, 16365492, 17252352, 25407252, 32617728, 42401268, 42966612, 54100800, 66163968, 71182800, 73019700
OFFSET
1,1
COMMENTS
Terms of this sequence must be of the form 13(6m)^2, the values for m are listed in A154775. - M. F. Hasler, Jan 15 2009
LINKS
FORMULA
a(n) = 468 A154775(n)^2 - M. F. Hasler, Jan 15 2009
MATHEMATICA
lst={}; Do[If[PrimeQ[n-1]&&PrimeQ[n+1], s=(n*13)^(1/2); If[Floor[s]==s, AppendTo[lst, n]]], {n, 6, 11!, 6}]; lst
(* ... and/or ... *)
lst={}; Do[If[PrimeQ[n-1]&&PrimeQ[n+1], s=(n/13)^(1/2); If[Floor[s]==s, AppendTo[lst, n]]], {n, 6, 11!, 6}]; lst
Select[13*Range[10^3]^2, And @@ PrimeQ[# + {-1, 1}] &] (* Amiram Eldar, Dec 25 2019 *)
PROG
(PARI) for(i=1, 499, isprime(468*i^2+1) && isprime(468*i^2-1) && print1(468*i^2", ")) \\ M. F. Hasler, Jan 15 2009
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from M. F. Hasler, Jan 15 2009
STATUS
approved