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Inconsummate numbers in base 10: no number is this multiple of the sum of its digits (in base 10).
(Formerly M5325)
21

%I M5325 #32 May 09 2023 19:03:55

%S 62,63,65,75,84,95,161,173,195,216,261,266,272,276,326,371,372,377,

%T 381,383,386,387,395,411,416,422,426,431,432,438,441,443,461,466,471,

%U 476,482,483,486,488,491,492,493,494,497,498,516,521,522,527,531,533,536

%N Inconsummate numbers in base 10: no number is this multiple of the sum of its digits (in base 10).

%D J. H. Conway, personal communication.

%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

%H Daniel Mondot, <a href="/A003635/b003635.txt">Table of n, a(n) for n = 1..10867</a>

%p For Maple code see A058906.

%t nmax = 1000; Reap[ Do[k = n; kmax = 100*n; While[ Tr[ IntegerDigits[k]]*n != k && k < kmax, k = k + n]; If[k == kmax, Sow[n]], {n, 1, nmax}]][[2, 1]] (* _Jean-François Alcover_, Jul 12 2012 *)

%o (Python)

%o from itertools import count, islice, combinations_with_replacement

%o def A003635_gen(startvalue=1): # generator of terms >= startvalue

%o for n in count(max(startvalue,1)):

%o for l in count(1):

%o if 9*l*n < 10**(l-1):

%o yield n

%o break

%o for d in combinations_with_replacement(range(10),l):

%o if (s:=sum(d))>0 and sorted(str(s*n)) == [str(e) for e in d]:

%o break

%o else:

%o continue

%o break

%o A003635_list = list(islice(A003635_gen(),20)) # _Chai Wah Wu_, May 09 2023

%Y Cf. A003634, A052489, A052490, A052491, A058898-A058917.

%K nonn,easy,nice,base

%O 1,1

%A _N. J. A. Sloane_ and _Mira Bernstein_