A057139 - OEIS

The OEIS is supported by the many generous donors to the OEIS Foundation.

A057139

Odd number of digits palindrome based on sequential digits.

1, 121, 12321, 1234321, 123454321, 12345654321, 1234567654321, 123456787654321, 12345678987654321, 1234567890987654321, 123456789010987654321, 12345678901210987654321, 1234567890123210987654321, 123456789012343210987654321, 12345678901234543210987654321

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

Andrew Howroyd, Table of n, a(n) for n = 1..100

FORMULA

a(n) = 10^n*A057137(n-1) + A057138(n) = 10^(n-1)*A057137(n) + A057138(n-1).

MATHEMATICA

Array[FromDigits@ Join[#, Reverse@ Most@ #] &@ Mod[Range[#], 10] &, 15] (* Michael De Vlieger, Jan 28 2020 *)

PROG

(PARI) a(n)={fromdigits(vector(2*n-1, i, if(i<=n, i, 2*n-i)%10))} \\ Andrew Howroyd, Jan 27 2020

CROSSREFS