|
|
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
|
|
|
FORMULA
|
|
|
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
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|