108 HISTORY OF THE THEOBY OF NUMBEKS. [CHAP.IV
If k is the least index for which /iftf^Xfc, M*—^ (mod p) for h<k} then A1""1 — ! is divisible by p*, but not by pl+k.
A. Palmstrom and A. Pollak15 proved that, if p is a prime and n, m are the exponents to which a belongs modulo py p2, respectively, then anp— 1 is divisible by p2, so that w is a multiple of n and a divisor of np, whence m=n or pn. Thus according as a?~~l is or is not =1 (mod p2), m=n or m=np.
Worms de Romilly150 noted that, if w is a primitive root of p2, the incongruent roots of x*~lz=l (mod p2) are co;p(j = l, . . ., p~l).
J. W. L. Glaisher16 proved that if r is a positive integer <p, p a prime,
where gn is the sum of the nth powers of
1 r1 ,1 2 r1
'f r+[(r~l)cr]; 2r+cr'' ' "'
(r being the least positive residue modulo r of —p. If /*>• is the least positive solution of ar/jii^i (mod r), viz., pjJLi+i=Q, then
gi^+^+ f m . +^=L+ J^+ J^+ mmt+ ^i  0i + Set Mr = 0, fjLi+3r =Mi Then

2,=0 (mod p). Sylvester's corrected results are proved. From (l+l)p,
For r'=r+kp, let>/ be the positive root of pju/+^=0 (mod r'). Then
r">i = l+felp+KVWp
It is shown that, for some integer t,
k k2 2^j5
(mod ^+3)<
k k k2 2k k2
 = *p, ^02s2^j5+2«s^ls (mod p),
Glaisher,17 using the same notations, gave
r^l+p(^++;..+fcl) (modp').
"L'interm^diaire des math., 8, 1901, 122, 2056 (7, 1900, 357).
1Bfljm, 2145.
16Quar. Jour. Math,, 32, 1901, 127, 240251.
"Messenger Math,, 30, 19001, 78.