OFFSET
1,2
COMMENTS
Inspired by Z. Seidov's post to the SeqFan list, cf. link. This yields A154672 as 180 a(n)^2. Indeed, if N is such that N/5 is a square, then M=5m^2 and this can't by the average of a twin prime pair unless m=6a.
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
Zak Seidov, "A154676", Jan 15 2009
FORMULA
a(n) = sqrt(A154672(n)/180)
MATHEMATICA
Select[Range[10^3], And @@ PrimeQ[180#^2 + {-1, 1}] &] (* Amiram Eldar, Dec 25 2019 *)
PROG
(PARI) for(i=1, 999, isprime(180*i^2+1) & isprime(180*i^2-1) & print1(i", "))
CROSSREFS
KEYWORD
nonn
AUTHOR
M. F. Hasler, Jan 15 2009
STATUS
approved