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

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

Alternative progression for n >= 10 compared with A002477.

Cf. A057137, A057138.

Sequence in context: A079215 A137466 A062689 * A321687 A002477 A173426

Adjacent sequences: A057136 A057137 A057138 * A057140 A057141 A057142

Keyword

base,easy,nonn

Author

Henry Bottomley, Aug 12 2000

Extensions

Terms a(13) and beyond from Andrew Howroyd, Jan 27 2020

Status

approved