OFFSET
1,1
COMMENTS
The sequence of first differences takes on the values {1, 2, 3} only, and each of these values occurs infinitely often (the values 1 and 2 are clear; for the value 3, note that consecutive numbers such as 199..9, 200..0 and 399..9, 400..0 that are excluded from the sequence occur infinitely often).
Nonnegative integers excluding those such that digits in their decimal representation share all the same parity. - R. J. Cano, Sep 10 2018
LINKS
R. J. Cano, PARI program
EXAMPLE
49 and 50 are in the sequence but 19 and 20 are not.
MATHEMATICA
Select[Range@ 122, Union[Mod[IntegerDigits[#], 2]] == {0, 1} &] (* Michael De Vlieger, Sep 04 2018 *)
PROG
(PARI) is(n) = my(d=digits(n), v=[]); if(n < 10, return(0)); for(k=1, #d, v=concat(v, [d[k]%2])); vecmin(v)!=vecmax(v) \\ Felix Fröhlich, Sep 01 2018
(PARI) See Cano link.
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
Enrique Navarrete, Aug 31 2018
STATUS
approved