OFFSET
1,2
LINKS
Pierre CAMI, Table of n, a(n) for n = 1..10000
EXAMPLE
1*1*9+1*3-1=11; 11 and 13 are twin primes so a(1)=1.
2*2*9+2*3-1=41; 41 and 43 are twin primes so a(2)=2.
MATHEMATICA
Select[Range[1000], AllTrue[9#^2+3#+{1, -1}, PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Feb 10 2019 *)
PROG
(PARI) s=[]; for(n=1, 1000, if(isprime(9*n^2+3*n-1) && isprime(9*n^2+3*n+1), s=concat(s, n))); s \\ Colin Barker, Feb 26 2014
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Pierre CAMI, Feb 25 2014
STATUS
approved