OFFSET
1,1
COMMENTS
Primes p such that 2*p+1, 4*p+3 and 8*p+7 are also primes. - Vincenzo Librandi, Aug 04 2010
For n > 2, a(n) == 29 (mod 30). - Zak Seidov, Jan 31 2013
LINKS
Nathaniel Johnston, Table of n, a(n) for n = 1..1000
MAPLE
p:=2: for n from 1 to 5000 do if(isprime(2*p+1) and isprime(4*p+3) and isprime(8*p+7))then printf("%d, ", p): fi: p:=nextprime(p): od: # Nathaniel Johnston, Jun 30 2011
MATHEMATICA
Select[Prime[Range[10^3*4]], PrimeQ[a1=2*#+1] && PrimeQ[a2=2*a1+1] && PrimeQ[a3=2*a2+1] &] (* Vladimir Joseph Stephan Orlovsky, May 01 2008 *)
Join[{2, 5}, Select[Range[89, 104369, 30], PrimeQ[#] && PrimeQ[2*# + 1] && PrimeQ[4*# + 3] && PrimeQ[8*# + 7] &]] (* Zak Seidov, Jan 31 2013 *)
p3iQ[n_]:=AllTrue[NestList[2#+1&, n, 3], PrimeQ]; Join[{2, 5}, Select[ Range[ 89, 200000, 30], p3iQ]] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Mar 30 2019 *)
PROG
(Magma) [n: n in [1..100000] | IsPrime(n) and IsPrime(2*n+1) and IsPrime(4*n+3) and IsPrime(8*n+7)] // Vincenzo Librandi, Aug 04 2010
(PARI) is(n)=isprime(n)&&isprime(2*n+1)&&isprime(4*n+3)&&isprime(8*n+7) \\ Charles R Greathouse IV, Mar 21 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved