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%I #8 Jan 28 2020 16:13:12
%S 1,121,12321,1234321,123454321,12345654321,1234567654321,
%T 123456787654321,12345678987654321,1234567890987654321,
%U 123456789010987654321,12345678901210987654321,1234567890123210987654321,123456789012343210987654321,12345678901234543210987654321
%N Odd number of digits palindrome based on sequential digits.
%H Andrew Howroyd, <a href="/A057139/b057139.txt">Table of n, a(n) for n = 1..100</a>
%F a(n) = 10^n*A057137(n-1) + A057138(n) = 10^(n-1)*A057137(n) + A057138(n-1).
%t Array[FromDigits@ Join[#, Reverse@ Most@ #] &@ Mod[Range[#], 10] &, 15] (* _Michael De Vlieger_, Jan 28 2020 *)
%o (PARI) a(n)={fromdigits(vector(2*n-1, i, if(i<=n, i, 2*n-i)%10))} \\ _Andrew Howroyd_, Jan 27 2020
%Y Alternative progression for n >= 10 compared with A002477.
%Y Cf. A057137, A057138.
%K base,easy,nonn
%O 1,2
%A _Henry Bottomley_, Aug 12 2000
%E Terms a(13) and beyond from _Andrew Howroyd_, Jan 27 2020
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