A193407 Mountain numbers (version 2).

1, 2, 3, 4, 5, 6, 7, 8, 9, 121, 131, 141, 151, 161, 171, 181, 191, 232, 242, 252, 262, 272, 282, 292, 343, 353, 363, 373, 383, 393, 454, 464, 474, 484, 494, 565, 575, 585, 595, 676, 686, 696, 787, 797, 898, 1231, 1241, 1251, 1261, 1271, 1281, 1291, 1321

Offset

1,2

Comments

Another version of mountain numbers (A134941).

For n > 9 the structure of digits represents a mountain. The first digit is equal to the last digit (1 - 9). The first digits are in increasing order. The last digits are in decreasing order. The numbers only have one largest digit. This sequence is finite. The final term is 12345678987654321.

Links

Table of n, a(n) for n=1..53.

Example

Illustration using the member of this sequence - number 56789765:
  .  .  .  .  9  .  .  .
  .  .  .  8  .  .  .  .
  .  .  7  .  .  7  .  .
  .  6  .  .  .  .  6  .
  5  .  .  .  .  .  .  5

Crossrefs

Supersequence of mountain numbers (A134941) and Giza numbers (A134810). Subsequence of hill numbers (A193408).

Sequence in context: A117228 A032567 A134853 * A134810 A173689 A004871

Adjacent sequences: A193404 A193405 A193406 * A193408 A193409 A193410

Keyword

nonn,base,fini

Author

Jaroslav Krizek, Jul 25 2011

Status

approved