|
|
A100020
|
|
a(n) = smallest prime p such that x^2-n has roots in the p-adic integers.
|
|
1
|
|
|
2, 7, 11, 2, 11, 5, 3, 7, 2, 3, 5, 11, 3, 5, 7, 2, 2, 7, 3, 11, 5, 3, 7, 5, 2, 5, 11, 3, 5, 7, 3, 7, 2, 3, 13, 2, 3, 11, 5, 3, 2, 11, 3, 5, 11, 3, 11, 11, 2, 7, 5, 3, 7, 5, 3, 5, 2, 3, 5, 7, 3, 13, 3, 2, 2, 5, 3, 2, 5, 3, 5, 7, 2, 5, 11
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
LINKS
|
|
|
EXAMPLE
|
a(6)=5 because x^2-6 has roots in the 5-adic integers. Roots are
4+5+4*5^2+2*5^4+3*5^5+2*5^6+5^7+3*5^8+O(5^9) and
1+3*5+4*5^3+2*5^4+5^5+2*5^6+3*5^7+5^8+O(5^9); but this is irreducible over Qp for p in {2,3} (x^2-6 is Eisenstein for p=2 and 3).
|
|
MAPLE
|
local p, anz ;
p := 1 ;
anz := 0 ;
while anz =0 do
p := nextprime(p) ;
poly := x^2-n ;
anz := nops([padic[rootp](poly, p)]);
end do:
p ;
end proc:
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Volker Schmitt (clamsi(AT)gmx.net), Nov 19 2004
|
|
STATUS
|
approved
|
|
|
|