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A242491 Numbers avoiding subtractive notation when written in Roman numerals. 0

%I

%S 1,2,3,5,6,7,8,10,11,12,13,15,16,17,18,20,21,22,23,25,26,27,28,30,31,

%T 32,33,35,36,37,38,50,51,52,53,55,56,57,58,60,61,62,63,65,66,67,68,70,

%U 71,72,73,75,76,77,78,80,81,82,83,85,86,87,88,100,101,102,103,105

%N Numbers avoiding subtractive notation when written in Roman numerals.

%C Numbers with only digits 0,1,2,3,5,6,7,8.

%C So this is a subsequence of A039145 with same number of 4 and 9: zero. - _Michel Marcus_, May 17 2014

%e 4 in Roman numerals is IV (5 - 1) and so 4 is not in this sequence.

%o (PARI) isok(n) = my(v = vecsort(digits(n))); ! (vecsearch(v, 4) || vecsearch(v, 9)); \\ _Michel Marcus_, May 19 2014

%K nonn,base,easy

%O 1,2

%A _J. Lowell_, May 16 2014

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Last modified September 21 21:58 EDT 2019. Contains 327282 sequences. (Running on oeis4.)