login
A089761
Smallest k such that k*i^2 + 1 is prime for i = 1 to n.
0
1, 1, 4, 22, 58, 58, 58, 54972, 68112, 4748632, 861066640, 861066640, 861066640, 861066640, 861066640
OFFSET
1,3
COMMENTS
a(16) > 1.4*10^13. [Max Alekseyev]
MAPLE
for n from 1 to 10 do for k from 1 do f:=0: for i from 1 to n do if not isprime(k*i^2+1) then f:=1: break fi od: if f=0 then printf("%d, ", k): break fi od od: # C. Ronaldo
CROSSREFS
Cf. A124417.
Sequence in context: A122241 A341375 A076525 * A098837 A104171 A036924
KEYWORD
hard,more,nonn
AUTHOR
Amarnath Murthy, Nov 22 2003
EXTENSIONS
Corrected and extended by C. Ronaldo (aga_new_ac(AT)hotmail.com), Dec 26 2004
a(11)-a(15) from Donovan Johnson, Sep 27 2008
STATUS
approved