

A290950


Positive integers whose digits are in increasing order and whose successive digits differ by exactly 2.


0



1, 2, 3, 4, 5, 6, 7, 8, 9, 13, 24, 35, 46, 57, 68, 79, 135, 246, 357, 468, 579, 1357, 2468, 3579, 13579
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OFFSET

1,2


COMMENTS

There are 11  2*k terms of the sequence with k digits, 1 <= k <= 5.


LINKS

Table of n, a(n) for n=1..25.


FORMULA

The terms can be described by the following linear equations:
for 1 <= n <= 9, a(n) = n;
for 10 <= n <= 16, a(n) = 11*(n  9) + 2;
for 17 <= n <= 21, a(n) = 111*(n  16) + 24;
for 22 <= n <= 24, a(n) = 1111*(n  21) + 246;
for n = 25, a(n) = 11111*(n  24) + 2468.


MATHEMATICA

Select[Range[10^5], Or[Length@ # == 1, Union@ Differences@ # == {2}] &@ IntegerDigits@ # &] (* Michael De Vlieger, Aug 15 2017 *)


CROSSREFS

Sequence in context: A034294 A304246 A271837 * A032577 A244155 A066310
Adjacent sequences: A290947 A290948 A290949 * A290951 A290952 A290953


KEYWORD

nonn,base,fini,full


AUTHOR

Enrique Navarrete, Aug 14 2017


STATUS

approved



