A247819 - OEIS

%I #16 Sep 05 2021 11:36:24

%S 7,11,13,14,17,19,21,22,23,26,28,29,33,34,35,37,38,39,41,42,43,44,46,

%T 47,48,49,51,52,53,55,56,57,58,59,61,62,63,65,66,67,68,69,70,71,73,74,

%U 76,77,78,79,82,83,84,85,86,87,88,89,91,92,93,94,95,96,97

%N Integers such that A247552(n) is not a repunit.

%C A247552(n) is the least number x such that the ratio of the sum of all the cyclic permutations of x, plus the unpermuted number, and x itself is equal to n.

%C When x is in the sequence, then all multiples of x are there too. The primitive terms, i.e., the terms that are not a multiple of a previous term, are 7, 11, 13, 17, 19, 23, 29, 37, 41, 43, 47, 48, 53, 59, 61, 62, ... Among those, one finds few composites: 48, 62, 93, 180, 675, 961, ...

%H Jens Kruse Andersen, <a href="/A247819/b247819.txt">Table of n, a(n) for n = 1..1000</a>

%e A247552(7) is 428571 instead of the more obvious 1111111, so 7 belongs to this sequence.

%o (PARI) lista() = my(v = readvec("b247552.txt")); select(x->vecmax(digits(x)) != 1, v, 1);

%Y Cf. A247552.

%K nonn,base

%O 1,1

%A _Michel Marcus_, Sep 24 2014