OFFSET
1,1
LINKS
K. D. Bajpai, Table of n, a(n) for n = 1..1013
EXAMPLE
a(1)=4: 4^2 + 1 = 17, 17 + 6 = 23 and 17 - 6 = 11; 11, 17 and 23 are primes.
MAPLE
with(StringTools): K := proc(x) local a, b; a:=(x^2+1); if (isprime(a)and isprime(a+6) and isprime(a-6) ) then RETURN (x) fi: end: seq(K(x), x=1..50000); # K. D. Bajpai, Jul 03 2013
K:=proc()local x, a, b, c; c:=1; for x from 1 to 1000000 do; a:=(x^2+1); if (isprime(a)and isprime(a+6) and isprime(a-6))then lprint(c, x); c:=c+1; fi; od; end: K(); # K. D. Bajpai, Jul 03 2013
PROG
(PARI) is(n)=isprime(n^2-5) && isprime(n^2+1) && isprime(n^2+7) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
K. D. Bajpai, Jul 03 2013
STATUS
approved