login
A128402
Numbers k such that k^2 divides 22^k-1.
15
1, 3, 7, 21, 39, 273, 507, 3081, 3549, 21567, 40053, 78117, 280371, 343239, 546819, 1015521, 2056899, 2402673, 5998317, 6171243, 7108647, 8740173, 12338859, 14398293, 18988203, 27115881, 41988219, 43198701, 47727771, 55431363
OFFSET
1,2
MAPLE
select(t -> 22 &^ t - 1 mod t^2 = 0, [seq(2*k+1, k=0..10^6)]); # Robert Israel, Jan 23 2015
MATHEMATICA
a={}; Do[r=(22^n-1)/n^2; If[r==IntegerPart[r], AppendTo[a, n]], {n, 1, 10^3}]; a (* Vladimir Joseph Stephan Orlovsky, Aug 07 2008 *)
PROG
(PARI) { forstep(m=11, 10^8, 2, if( Mod(22, m^2)^m==1, print(m) ) ) } \\ Max Alekseyev, Oct 18 2008
KEYWORD
nonn,less
AUTHOR
Alexander Adamchuk, Mar 01 2007
EXTENSIONS
a(14)-a(30) from Max Alekseyev, Oct 18 2008
STATUS
approved