OFFSET
1,1
COMMENTS
All the terms in the sequence are congruent to 1 mod 6.
The constants in the definition (4, 444 and 4444) are the concatenations of the digit 4.
LINKS
K. D. Bajpai, Table of n, a(n) for n = 1..10000
EXAMPLE
a(1) = 13 is a prime: 13+4 = 17, 13+444 = 457 and 13+4444 = 4457 are also prime.
a(2) = 19 is a prime: 19+4 = 23, 19+444 = 463 and 19+4444 = 4463 are also prime.
MAPLE
KD:= proc() local a, b, d, e; a:= ithprime(n); b:=a+4; d:=a+444; e:=a+4444; if isprime(b)and isprime(d)and isprime(e)then return (a): fi; end: seq(KD(), n=1..5000);
MATHEMATICA
KD = {}; Do[p = Prime[n]; If[PrimeQ[p + 4] && PrimeQ[p + 444] && PrimeQ[p + 4444], AppendTo[KD, p]], {n, 5000}]; KD
(* For the b-file*) c = 0; p = Prime[n]; Do[If[PrimeQ[p + 4] && PrimeQ[p + 444] && PrimeQ[p + 4444], c = c + 1; Print[c, " ", p]], {n, 1, 3*10^6}];
PROG
(PARI) s=[]; forprime(p=2, 12000, if(isprime(p+4) && isprime(p+444) && isprime(p+4444), s=concat(s, p))); s \\ Colin Barker, Apr 25 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
K. D. Bajpai, Apr 23 2014
STATUS
approved