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A336880
Numbers with decimal expansion d_1, ..., d_w such that for any k in 1..w there is some m in 1..w such that d_k = d_m = abs(k - m).
3
0, 11, 110, 111, 202, 1100, 1110, 1111, 2020, 2222, 3003, 3113, 11000, 11011, 11100, 11110, 11111, 11202, 20200, 20202, 20211, 22220, 22222, 23203, 30030, 30232, 31130, 33033, 40004, 40114, 41104, 41114, 42024, 110000, 110011, 110110, 110111, 110202, 111000
OFFSET
1,2
COMMENTS
This sequence has similarities with A336668.
All repunits (A002275) belong to this sequence.
The concatenation of two terms is also a term.
The digit reversal (A004086) of a term is also a term.
For any d in 1..9, d * (1 + 10^d) is the first term containing the digit d.
LINKS
EXAMPLE
Regarding 30232:
- the first digit 3 is 3 positions away from the second digit 3 and vice versa,
- the digit 0 matches itself,
- the first digit 2 is 2 positions away from the second digit 2 and vice versa,
- so 30232 belongs to this sequence.
PROG
(PARI) is(n, base=10) = { my (d=digits(n, base)); for (k=1, #d, if ((k-d[k]<1 || d[k-d[k]]!=d[k]) && (k+d[k]>#d || d[k+d[k]]!=d[k]), return (0)));
return (1) }
CROSSREFS
Cf. A002275, A144795 (binary analog), A336668.
Sequence in context: A280855 A103542 A293871 * A211968 A284040 A288293
KEYWORD
nonn,base
AUTHOR
Rémy Sigrist, Aug 06 2020
STATUS
approved