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A138141
Numbers with digits in ascending order that differ exactly by 1.
6
1, 2, 3, 4, 5, 6, 7, 8, 9, 12, 23, 34, 45, 56, 67, 78, 89, 123, 234, 345, 456, 567, 678, 789, 1234, 2345, 3456, 4567, 5678, 6789, 12345, 23456, 34567, 45678, 56789, 123456, 234567, 345678, 456789, 1234567, 2345678, 3456789, 12345678, 23456789, 123456789
OFFSET
1,2
COMMENTS
This finite sequence has 45 members. The last member is 123456789. There are 10-k members with k digits. See A052017 for primes in this sequence. All members with 3 or more digits are straight-line numbers A135643.
FORMULA
a(n) = floor(((9*t^2 - 189*t + 18*n + 182) * (10^t - 1) - 18*t) / 162), where t = floor((21 - sqrt(369 - 8*n)) / 2). - Christopher J. Thomas, Feb 14 2024
MATHEMATICA
Table[FromDigits/@Partition[Range[9], n, 1], {n, 9}]//Flatten (* Harvey P. Dale, Mar 19 2017 *)
CROSSREFS
KEYWORD
base,easy,fini,full,nonn
AUTHOR
Omar E. Pol, Mar 19 2008
STATUS
approved