login
A207830
Positive multiples of 3 that contain the decimal digit 1.
0
12, 15, 18, 21, 51, 81, 102, 105, 108, 111, 114, 117, 120, 123, 126, 129, 132, 135, 138, 141, 144, 147, 150, 153, 156, 159, 162, 165, 168, 171, 174, 177, 180, 183, 186, 189, 192, 195, 198, 201, 210, 213, 216, 219, 231, 261, 291, 312, 315, 318, 321, 351, 381, 411, 414
OFFSET
1,1
COMMENTS
I came across this sequence while working some problems in ALCUMUS from the AoPS site. [Tyler]
A 10-automatic set: members are numbers with decimal expansions matching a regular expression. - Charles R Greathouse IV, Feb 20 2012
REFERENCES
MathCounts 2006 National Target #5
MATHEMATICA
Select[3*Range[138], DigitCount[#, 10, 1] > 0 &] (* Alonso del Arte, Feb 20 2012 *)
PROG
(PARI) is(n)=if(n%3, return(0)); n=vecsort(eval(Vec(Str(n))), , 8); n[1]==1||(#n>1&&n[2]==1) \\ Charles R Greathouse IV, Feb 20 2012
(PARI) is(n)=n%3==0 && setsearch(Set(digits(n)), 1) \\ Charles R Greathouse IV, Feb 12 2017
CROSSREFS
Sequence in context: A265128 A243021 A164782 * A348788 A101171 A329731
KEYWORD
nonn,base,easy
AUTHOR
Seth Tyler, Feb 20 2012
EXTENSIONS
a(7)-a(55) from Charles R Greathouse IV, Feb 20 2012
STATUS
approved