A213341 - OEIS

%I #17 Jun 13 2012 17:55:48

%S 0,55,686,6996,79897,799997,8998998,89999998,999989999,9999999999

%N Smallest palindrome with digital root n and n + 1 decimal digits.

%C Formula a(n) = (44/9*(10^n-1)+(10^n+1)*n) gives for n=0 ... 5 another sequence of palindromic terms a(0) = 0, a(1) = 55, a(2) = 686, a(3) = 7887, a(4) = 88888, a(5) = 988889 (which do not fully comply with the definition "smallest palindrome with digital root n and n+1 decimal digits" - because for n = 3, 4, 5 the terms are not the smallest ones possible).

%e a(1) = 55 because there is no smaller two digit palindrome with a digital root of 1.

%Y Subsequence of A062388.

%K nonn,base,fini,full

%O 0,2

%A _Alexander R. Povolotsky_, Jun 09 2012