A138141 Numbers with digits in ascending order that differ exactly by 1.

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.

Links

Table of n, a(n) for n=1..45.

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

Cf. A052017, A059043, A135643, A138142.

Sequence in context: A200372 A059043 A259236 * A228017 A346535 A227224

Adjacent sequences: A138138 A138139 A138140 * A138142 A138143 A138144

Keyword

base,easy,fini,full,nonn

Author

Omar E. Pol, Mar 19 2008

Status

approved