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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 Table of n, a(n) for n=1..19. 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 Cf. A062970, A001923. Sequence in context: A138268 A031444 A031033 * A212748 A032828 A193379 Adjacent sequences: A128978 A128979 A128980 * A128982 A128983 A128984 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.)