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A128981 Numbers k such that k divides Sum_{j=1..k} j^j = A001923(k). 7
1, 4, 17, 19, 148, 1577, 3564, 4388, 5873, 6639, 8579, 62500, 376636, 792949, 996044, 1174065, 3333551, 5179004, 7516003 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
a(20) > 10^7. - Hiroaki Yamanouchi, Aug 25 2015
LINKS
MAPLE
a:=0:
for n from 1 to 2000 do
a:=a+n^n:
if a mod n=0 then
print(n);
fi;
od: # Revised program from R. J. Mathar, Jun 18 2015
MATHEMATICA
f=0; Do[ f=f+k^k; If[ IntegerQ[f/k], Print[k] ], {k, 1, 6639} ]
PROG
(PARI) for(n=1, 10^4, s=sum(i=1, n, Mod(i, n)^i); if(!Mod(s, n), print1(n, ", "))) \\ Derek Orr, Jun 18 2015
(Python)
from itertools import accumulate, count, islice
def A128981_gen(): # generator of terms
yield 1
for i, j in enumerate(accumulate(k**k for k in count(1)), start=2):
if j % i == 0:
yield i
A128981_list = list(islice(A128981_gen(), 10)) # Chai Wah Wu, Jun 18 2022
CROSSREFS
Sequence in context: A138268 A031444 A031033 * A212748 A032828 A193379
KEYWORD
hard,more,nonn
AUTHOR
Alexander Adamchuk, Apr 29 2007
EXTENSIONS
a(11) and a(12) from Jon E. Schoenfield, May 09 2007
a(13) = 376636 from Alexander Adamchuk, May 03 2010
a(14)-a(16) from Lars Blomberg, May 10 2011
a(17) from Giovanni Resta, Jul 13 2015
a(18)-a(19) from Hiroaki Yamanouchi, Aug 25 2015
STATUS
approved

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Last modified April 25 07:07 EDT 2024. Contains 371964 sequences. (Running on oeis4.)