OFFSET
1,1
COMMENTS
The first negative term is a(20750) = -58207896.
All terms are divisible by 8.
LINKS
Robert Israel, Table of n, a(n) for n = 1..30000
EXAMPLE
The first primes == 1, 3, 5, 7 (mod 8) are 17, 3, 5, 7 respectively, so a(1) = 17*7 - 3*5 = 104.
The second primes == 1, 3, 5, 7 (mod 8) are 41, 11, 13, 23 respectively, so a(2) = 41*23 - 11*13 = 800.
The third primes == 1, 3, 5, 7 (mod 8) are 73, 19, 29, 31 respectively, so a(3) = 73*31 - 19*29 = 1712.
MAPLE
R:= NULL:
L:= [-7, -5, -3, -1]:
found:= false:
for k from 1 to 100 do
for i from 1 to 4 do
for x from L[i]+8 by 8 do until isprime(x);
L[i]:= x;
od;
v:= L[1]*L[4]-L[2]*L[3];
R:= R, v;
od:
R;
CROSSREFS
KEYWORD
sign,look
AUTHOR
J. M. Bergot and Robert Israel, Jan 27 2021
STATUS
approved