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 A154670 Averages of twin prime pairs k such that k*2 and k/2 are squares. 10
 18, 72, 882, 1152, 2592, 3528, 4050, 15138, 20808, 34848, 46818, 69192, 83232, 103968, 112338, 149058, 176418, 180000, 206082, 281250, 362952, 388962, 438048, 472392, 478242, 538722, 649800, 734472, 808992, 960498, 1080450, 1143072 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Amiram Eldar, Table of n, a(n) for n = 1..10000 FORMULA a(n) = 18*A037073(n)^2. - M. F. Hasler, Jan 15 2009 EXAMPLE 18/2 = 9 = 3^2, 18*2 = 36 = 6^2. MATHEMATICA lst={}; Do[If[PrimeQ[n-1]&&PrimeQ[n+1], s=Sqrt[n*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=Sqrt[n/2]; If[Floor[s]==s, AppendTo[lst, n]]], {n, 6, 10!, 6}]; lst PROG (PARI) for(i=1, 999, isprime(18*i^2+1) && isprime(18*i^2-1) && print1(18*i^2", ")) \\ M. F. Hasler, Jan 15 2009 CROSSREFS Cf. A037073. Sequence in context: A007276 A052619 A110753 * A041626 A039608 A211619 Adjacent sequences:  A154667 A154668 A154669 * A154671 A154672 A154673 KEYWORD nonn AUTHOR Vladimir Joseph Stephan Orlovsky, Jan 13 2009 STATUS approved

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Last modified September 22 21:04 EDT 2021. Contains 347608 sequences. (Running on oeis4.)