A227178 Numbers k such that p = k^2 + 1 is prime, as are p-6 and p+6.

4, 6, 16, 36, 74, 116, 176, 184, 654, 1276, 1314, 1394, 1524, 1546, 1686, 2676, 3074, 3196, 3314, 3504, 3534, 3624, 3884, 4026, 4034, 4384, 4414, 4786, 5486, 5566, 5874, 5996, 6434, 6984, 7404, 7466, 7536, 7596, 8304, 8894, 9386, 10086, 11056, 11204, 12386

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

Sequence in context: A162485 A188466 A076066 * A165799 A231998 A056421

Adjacent sequences: A227175 A227176 A227177 * A227179 A227180 A227181

Keyword

nonn,easy

Author

K. D. Bajpai, Jul 03 2013

Status

approved