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A308365 Numbers which are products of repunits.

%I A308365 #73 Jan 17 2022 10:03:10
%S A308365 1,11,111,121,1111,1221,1331,11111,12221,12321,13431,14641,111111,
%T A308365 122221,123321,134431,135531,147741,161051,1111111,1222221,1233321,
%U A308365 1234321,1344431,1356531,1367631,1478741,1490841,1625151,1771561,11111111,12222221,12333321
%N A308365 Numbers which are products of repunits.
%C A308365 The number of terms below 10^n is A216053(n)-1 for 1 <= n <= 25, but not for larger n. - _Rémy Sigrist_, May 28 2019
%C A308365 The product of repunits is not necessarily palindromic, see A339676. - _Bernard Schott_, Apr 02 2021
%H A308365 Robert Israel, <a href="/A308365/b308365.txt">Table of n, a(n) for n = 1..10000</a>
%e A308365 a(11) = 13431 is in the sequence since it is the product of repunits (11^2*111).
%p A308365 d:= 10: # for terms < 10^d
%p A308365 N:= 10^d:
%p A308365 S:= {1}:
%p A308365 for m from 2 to d do
%p A308365   r:= (10^m-1)/9;
%p A308365   k:= floor(log[r](N));
%p A308365   V:= S;
%p A308365   for i from 1 to k do
%p A308365     V:= select(`<`,map(`*`,V,r),N);
%p A308365     S:= S union V
%p A308365   od;
%p A308365 od:
%p A308365 sort(convert(S,list)); # _Robert Israel_, Nov 26 2020
%Y A308365 Cf. A002275 (repunits), A083278 (repunit powers), A216053, A339676 (nonpalindromic terms).
%K A308365 nonn,base
%O A308365 1,2
%A A308365 _Sergio Pimentel_, May 22 2019
%E A308365 Missing a(25) = 1356531 inserted by _Ilya Gutkovskiy_, Apr 14 2020