login
A226967
Numbers n such that 1^n + 2^n + 3^n + ... + n^n == 9 (mod n).
11
1, 2, 3, 9, 54, 378, 16254
OFFSET
1,2
COMMENTS
Also, numbers n such that B(n)*n == 9 (mod n), where B(n) is the n-th Bernoulli number. Equivalently, SUM[prime p, (p-1) divides n] n/p == -9 (mod n). There are no other terms below 10^30. - Max Alekseyev, Aug 26 2013
MATHEMATICA
Select[Range[10000], Mod[Sum[PowerMod[i, #, #], {i, #}], #] == Mod[9, #] &]
PROG
(PARI) is(n)=Mod(sumdiv(n, d, if(isprime(d+1), n/(d+1))), n)==-9 \\ Charles R Greathouse IV, Nov 13 2013
CROSSREFS
Cf. A031971.
Solutions to 1^n+2^n+...+n^n == m (mod n): A005408 (m=0), A014117 (m=1), A226960 (m=2), A226961 (m=3), A226962(m=4), A226963 (m=5), A226964 (m=6), A226965 (m=7), A226966 (m=8), this sequence (m=9), A280041 (m=19), A280043 (m=43), A302343 (m=79), A302344 (m=193).
Sequence in context: A255739 A037389 A037425 * A181273 A270394 A120032
KEYWORD
nonn,more
AUTHOR
EXTENSIONS
1,2,9 prepended by Max Alekseyev, Aug 26 2013
STATUS
approved