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This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

User: Clive Stott

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A275220 a(n) is the smallest integer with at least n palindromic representations of length >= 3 in bases b >= 2.

Original entry on oeis.org

5, 17, 65, 121, 562, 1432, 1477, 4369, 35101, 35101, 83161, 83161, 291721, 291721, 720721, 887041, 1496881, 1670761, 3341521, 3341521, 5654881, 7207201, 7761601, 10810801, 12252241, 15135121, 21621601, 28274401, 28274401, 41081041, 41081041, 41081041
Offset: 1

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Author

Clive Stott, Jul 20 2016

Keywords

Comments

a(9) and a(10) are identical because there is no number less than 35101 with nine palindromic representations in different bases; likewise for a(11) and a(12), and for a(13) and a(14).

Crossrefs

Cf. A123586.

Programs

  • PARI
    isok(k, n) = sum(b=2, k-1, (d=digits(k,b)) && (#d >= 3) && (Vecrev(d) == d)) >= n;
a(n) = my(j=1); while(! isok(j, n), j++); j; \\ Michel Marcus, Jul 28 2016

Extensions

a(17)-a(32) from Giovanni Resta, Jul 28 2016

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