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A110400 a(1) = 1, a(2) = 21; for n>2, a(n) is the least number whose neighboring digit difference forms a(n-1) such that a(n+1) also exists. 0

%I

%S 1,21,132,1031,10032,100031,1000032,10000031,100000032,1000000031,

%T 10000000032,100000000031,1000000000032,10000000000031,

%U 100000000000032,1000000000000031,10000000000000032,100000000000000031

%N a(1) = 1, a(2) = 21; for n>2, a(n) is the least number whose neighboring digit difference forms a(n-1) such that a(n+1) also exists.

%C a(2) = 21 (chosen) and not 10 so that the sequence extends nontrivially.

%C A040115(a(n+1)) = a(n). - _David Wasserman_, Oct 02 2005

%e After 8421 two possible candidates are 91532 and 91576 but there is no number with digit difference 91576 hence the next term is 91532.

%e 1031 is followed by 10032 because the absolute differences between the numbers 1, 0, 0, 3, 2 are 1, 0, 3, 1.

%Y Cf. A011557.

%K base,easy,nonn

%O 1,2

%A _Amarnath Murthy_, Jul 29 2005

%E Corrected and extended by _David Wasserman_, Oct 02 2005

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Last modified January 17 04:08 EST 2022. Contains 350377 sequences. (Running on oeis4.)