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A236689
The sum of two neighboring digits is a palindrome; a(n) is the smallest possible nonnegative integer not occurring earlier.
1
0, 1, 2, 3, 4, 5, 6, 10, 7, 11, 8, 12, 9, 20, 13, 14, 15, 16, 17, 18, 30, 21, 22, 23, 24, 25, 26, 27, 29, 200, 31, 32, 33, 34, 35, 36, 38, 100, 40, 41, 42, 43, 44, 45, 47, 101, 50, 51, 52, 53, 54, 56, 102, 60, 61, 62, 63, 65, 103, 80, 70, 71, 72, 74, 104
OFFSET
0,3
COMMENTS
The sum of two digits is a palindrome iff it is less than 10 or equal to 11. Therefore, numbers with substrings 19, 28, 37, 39, 46, ... (this is not A065207) can never occur, and this is not a permutation of the nonnegative integers.
LINKS
E. Angelini, Palindromes -- with digits, SeqFan List, Jan 27 2014.
PROG
(PARI) a=u=0; (isp(s)=s<10||s==11); for(n=1, 100, print1(a", "); u+=1<<a; for(k=1, 9e9, bittest(u, k)&&next; for(j=1, #d=digits(k), isp(if(j>1, d[j-1], a%10)+d[j])&&next; k=(k\10^(#d-j)+1)*10^(#d-j)-1; next(2)); a=k; break))
CROSSREFS
Cf. A228730.
Sequence in context: A194913 A194864 A131829 * A308719 A026266 A334389
KEYWORD
nonn,base
AUTHOR
Eric Angelini and M. F. Hasler, Jan 29 2014
STATUS
approved