cp's OEIS Frontend

A257220 Numbers that have at least one divisor containing the digit 3 in base 10.

%I A257220 #21 Jun 06 2025 19:09:44
%S A257220 3,6,9,12,13,15,18,21,23,24,26,27,30,31,32,33,34,35,36,37,38,39,42,43,
%T A257220 45,46,48,51,52,53,54,57,60,62,63,64,65,66,68,69,70,72,73,74,75,76,78,
%U A257220 81,83,84,86,87,90,91,92,93,96,99,102,103,104,105,106,108
%N A257220 Numbers that have at least one divisor containing the digit 3 in base 10.
%C A257220 Numbers k whose concatenation of divisors A037278(k), A176558(k), A243360(k) or A256824(k) contains a digit 3.
%C A257220 Sequences of numbers k whose concatenation of divisors contains a digit j in base 10 for 0 <= j <= 9: A209932 for j = 0, A000027 for j = 1, A257219 for j = 2, A257220 for j = 3, A257221 for j = 4, A257222 for j = 5, A257223 for j = 6, A257224 for j = 7, A257225 for j = 8, A257226 for j = 9.
%H A257220 Charles R Greathouse IV, <a href="/A257220/b257220.txt">Table of n, a(n) for n = 1..10000</a>
%F A257220 a(n) ~ n. - _Charles R Greathouse IV_, Apr 30 2015
%e A257220 18 is in sequence because the list of divisors of 18: (1, 2, 3, 6, 9, 18) contains digit 3.
%t A257220 Select[Range@108, Part[Plus @@ DigitCount@ Divisors@ #, 3] > 0 &] (* _Michael De Vlieger_, Apr 20 2015 *)
%o A257220 (Magma) [n: n in [1..1000] | [3] subset Setseq(Set(Sort(&cat[Intseq(d): d in Divisors(n)])))];
%o A257220 (PARI) is(n)=fordiv(n,d, if(setsearch(Set(digits(d)),3), return(1))); 0 \\ _Charles R Greathouse IV_, Apr 30 2015
%Y A257220 Cf. A037278, A176558, A243360, A256824.
%K A257220 nonn,base
%O A257220 1,1
%A A257220 _Jaroslav Krizek_, Apr 20 2015