login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 26 17:47 EDT 2022. Contains 357002 sequences. (Running on oeis4.)