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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. 0
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 (list; graph; refs; listen; history; text; internal format)
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

Table of n, a(n) for n=0..64.

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 A075163

Adjacent sequences:  A236686 A236687 A236688 * A236690 A236691 A236692

KEYWORD

nonn,base

AUTHOR

Eric Angelini and M. F. Hasler, Jan 29 2014

STATUS

approved

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Last modified November 22 16:31 EST 2019. Contains 329396 sequences. (Running on oeis4.)