OFFSET
1,1
COMMENTS
This sequence was suggested by Moshe Shmuel Newman. It has its source in his study of finite groups.
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..10000
EXAMPLE
Prime p = 7 is in the sequence because q = 4*7+1 = 29 and r = (2*7+1)/3 = 5 are also primes.
MAPLE
a:= proc(n) option remember; local p; p:= `if`(n=1, 1, a(n-1));
do p:= nextprime(p); if irem(p, 3)=1 and
isprime(4*p+1) and isprime((2*p+1)/3) then break fi
od; p
end:
seq(a(n), n=1..50); # Alois P. Heinz, Jan 07 2018
MATHEMATICA
a[n_] := a[n] = Module[{p}, p = If[n == 1, 1, a[n-1]]; While[True, p = NextPrime[p]; If[Mod[p, 3] == 1 && PrimeQ[4p+1] && PrimeQ[(2p+1)/3], Break[]]]; p];
Array[a, 50] (* Jean-François Alcover, Nov 27 2020, after Alois P. Heinz *)
PROG
(PARI) isok(p) = isprime(p) && isprime(4*p+1) && iferr(isprime((2*p+1)/3), E, 0); \\ Michel Marcus, Nov 27 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
David S. Newman, Jan 04 2018
EXTENSIONS
More terms from Alois P. Heinz, Jan 07 2018
STATUS
approved