OFFSET
1,1
COMMENTS
Sequence a(k)*(a(k)+2) = 8, 15, 24, 35, 80, 99, ... equals A069826.
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
20*22 = 440; both 440-21 = 419 and 440+21 = 461 are prime, hence 20 is a term.
MAPLE
select(n -> isprime(n^2+n-1) and isprime(n^2+3*n+1), [$1..1000]); # Robert Israel, Jun 11 2018
MATHEMATICA
Select[Range@ 475, AllTrue[{# (# + 2) - (# + 1), # (# + 2) + (# + 1)}, PrimeQ] &] (* Michael De Vlieger, Jun 11 2018 *)
PROG
(Magma) [ n: n in [1..500] | IsPrime(n*(n+2)+(n+1)) and IsPrime(n*(n+2)-(n+1)) ]; /* Klaus Brockhaus, Apr 17 2007 */
CROSSREFS
KEYWORD
nonn
AUTHOR
J. M. Bergot, Apr 16 2007
EXTENSIONS
Edited and extended by Klaus Brockhaus, Apr 17 2007
STATUS
approved