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A160677 Numbers k such that k, 2k and 3k use the same number of characters when expressed in Roman numerals. 4

%I

%S 2,7,20,22,36,70,72,97,153,200,202,207,220,222,236,315,351,360,362,

%T 379,448,653,700,702,707,720,722,736,871,970,972,997,1035,1087,1177,

%U 1235,1267,1350,1352,1357,1386,1537,1677,1735,1767,1818,1836,1870,1872,1897

%N Numbers k such that k, 2k and 3k use the same number of characters when expressed in Roman numerals.

%C 2 = II, 4 = IV, 6 = VI;

%C 7 = VII, 14 = XIV, 21 = XXI;

%C 20 = XX, 40 = XL, 60 = LX.

%H Nathaniel Johnston, <a href="/A160677/b160677.txt">Table of n, a(n) for n = 1..57</a> (complete up to 3999)

%p for n from 1 to 3999 do if(length(convert(n, roman)) = length(convert(2*n, roman)) and length(convert(n, roman)) = length(convert(3*n, roman)))then printf("%d, ", n): fi: od: # _Nathaniel Johnston_, May 18 2011

%Y Cf. A006968.

%K nonn,easy

%O 1,1

%A _Claudio Meller_, May 23 2009, May 24 2009

%E Extended by _Nathaniel Johnston_, May 18 2011

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Last modified December 2 02:12 EST 2021. Contains 349435 sequences. (Running on oeis4.)