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%I #34 Jan 22 2023 02:37:41
%S 1,2,3,13,8,6,15,12,28,18,24,32,36,30,54,42,78,100,72,176,60,208,84,
%T 132,160,198,120,204,216,308,168,280,306,180,210,264,270,252,378,336,
%U 300
%N Index of smallest repunit having exactly n prime factors (counted with multiplicity).
%C a(40) = 300; all other subsequent terms are > 322. - _Ray Chandler_, Apr 23 2017
%C a(41) <= 684, a(42) <= 546, a(43) <= 528, a(44) <= 462, a(45) = 360, a(46) <= 576, a(47) <= 624, a(48) <= 768. - _Daniel Suteu_, Jan 21 2023
%H Patrick De Geest, <a href="http://www.worldofnumbers.com/repunits.htm">Repunits prime factors</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Repunit.html">Repunit</a>
%e For n = 5: R_6 = 111111 = 3*7*11*13*37 is the smallest repunit with five prime factors, so a(5) = 6.
%o (PARI) a(n) = my(k=1); while(bigomega((10^k - 1)/9) !=n, k++); k; \\ _Michel Marcus_, Apr 23 2017
%Y Cf. A000042, A001222, A002275, A004022, A046053.
%Y Initial terms of A004023, A046413, A046414, A046415, A046416, A046417, A046418, A046419.
%Y Cf. A086565 (equivalent with distinct prime factors).
%K nonn,more
%O 0,2
%A _Patrick De Geest_, Jul 15 1998
%E a(1) = 2 inserted and a(19)-a(37) added by _Ray Chandler_, Apr 23 2017
%E a(38)-a(40) from _Jinyuan Wang_, Apr 17 2020
%E Name corrected by _Felix Fröhlich_, Jun 04 2022