cp's OEIS Frontend

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).

%I A336880 #9 Aug 11 2020 20:52:41
%S A336880 0,11,110,111,202,1100,1110,1111,2020,2222,3003,3113,11000,11011,
%T A336880 11100,11110,11111,11202,20200,20202,20211,22220,22222,23203,30030,
%U A336880 30232,31130,33033,40004,40114,41104,41114,42024,110000,110011,110110,110111,110202,111000
%N 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).
%C A336880 This sequence has similarities with A336668.
%C A336880 All repunits (A002275) belong to this sequence.
%C A336880 The concatenation of two terms is also a term.
%C A336880 The digit reversal (A004086) of a term is also a term.
%C A336880 For any d in 1..9, d * (1 + 10^d) is the first term containing the digit d.
%H A336880 Rémy Sigrist, <a href="/A336880/b336880.txt">Table of n, a(n) for n = 1..10000</a>
%e A336880 Regarding 30232:
%e A336880 - the first digit 3 is 3 positions away from the second digit 3 and vice versa,
%e A336880 - the digit 0 matches itself,
%e A336880 - the first digit 2 is 2 positions away from the second digit 2 and vice versa,
%e A336880 - so 30232 belongs to this sequence.
%o A336880 (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)));
%o A336880 return (1) }
%Y A336880 Cf. A002275, A144795 (binary analog), A336668.
%K A336880 nonn,base
%O A336880 1,2
%A A336880 _Rémy Sigrist_, Aug 06 2020