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

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

Author

Clive Stott, Jul 20 2016

Keywords

• base
• nonn

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