A242491 Numbers avoiding subtractive notation when written in Roman numerals.

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, 32, 33, 35, 36, 37, 38, 50, 51, 52, 53, 55, 56, 57, 58, 60, 61, 62, 63, 65, 66, 67, 68, 70, 71, 72, 73, 75, 76, 77, 78, 80, 81, 82, 83, 85, 86, 87, 88, 100, 101, 102, 103, 105

Offset

1,2

Comments

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

So this is a subsequence of A039145 with same number of 4 and 9: zero. - Michel Marcus, May 17 2014

Links

Table of n, a(n) for n=1..68.

Example

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

Prog

(PARI) isok(n) = my(v = vecsort(digits(n))); ! (vecsearch(v, 4) || vecsearch(v, 9)); \\ Michel Marcus, May 19 2014
(Python)
from itertools import count, islice
from sympy.ntheory.factor_ import digits
def A242491_gen(): # generator of terms
    return (int(''.join(str(d) if d<4 else str(d+1) for d in digits(n, 8)[1:])) for n in count(1))
A242491_list = list(islice(A242491_gen(), 40)) # Chai Wah Wu, Mar 05 2024

Crossrefs

Sequence in context: A184514 A001068 A039145 * A038129 A062071 A087069

Adjacent sequences: A242488 A242489 A242490 * A242492 A242493 A242494

Keyword

nonn,base,easy

Author

J. Lowell, May 16 2014

Status

approved