OFFSET
1,1
LINKS
David Consiglio, Jr. and T. D. Noe, Table of n, a(n) for n = 1..1000
EXAMPLE
47 is prime, so is (47-1)/2=23 and also 6*47+1=283; 83 is a prime, (83-1)/2=41 and 6*83+1=499, ...
MAPLE
ts_sg_var_pras := proc(nmax) local i, tren, atek; tren := 0: for i from 1 to nmax do atek := numtheory[safeprime](i): if (atek > tren) then if (isprime(atek)='true' and isprime(6*atek+1)='true') then tren := atek: fi; fi; od; end: seq(ts_sg_var_pras(i), i=1..3000);
MATHEMATICA
Select[Range[20000], PrimeQ[#] && PrimeQ[(#-1)/2] && PrimeQ[6#+1] &] (* T. D. Noe, Nov 07 2011 *)
Select[Prime[Range[1700]], And@@PrimeQ[{(#-1)/2, 6#+1}]&] (* Harvey P. Dale, Feb 28 2013 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Jani Melik, Oct 02 2002
STATUS
approved