This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A257219 #30 Sep 08 2022 08:46:12 %S A257219 2,4,6,8,10,12,14,16,18,20,21,22,23,24,25,26,27,28,29,30,32,34,36,38, %T A257219 40,42,44,46,48,50,52,54,56,58,60,62,63,64,66,68,69,70,72,74,75,76,78, %U A257219 80,81,82,84,86,87,88,90,92,94,96,98,100,102,104,105,106,108 %N A257219 Numbers that have at least one divisor containing the digit 2 in base 10. %C A257219 Numbers k whose concatenation of divisors A037278(k), A176558(k), A243360(k) or A256824(k) contains a digit 2. %C A257219 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. %C A257219 All even numbers and all numbers which have a digit "2" themselves are trivially in this sequence. The first terms not of this form are the odd multiples of odd numbers between 21 and 29: { 63 = 3*21, 69 = 3*23, 75 = 3*25, 81 = 3*27, 87 = 3*29, 105 = 5*21, 115 = 5*23, 135 = 5*27, 145 = 5*29, ...}. - _M. F. Hasler_, Apr 22 2015 %C A257219 A011532 (numbers that contain a 2) is a subsequence. - _Michel Marcus_, May 19 2015 %H A257219 Charles R Greathouse IV, <a href="/A257219/b257219.txt">Table of n, a(n) for n = 1..10000</a> %F A257219 a(n) ~ n. - _Charles R Greathouse IV_, Apr 22 2015 %e A257219 18 is in sequence because the list of divisors of 18: (1, 2, 3, 6, 9, 18) contains digit 2. %e A257219 In the same way all even numbers have the divisor 2 and thus are in this sequence; numbers N in { 20,...,29, 120,...,129, 200,...,299 } have the digit 2 in N which is divisor of itself. - _M. F. Hasler_, Apr 22 2015 %t A257219 Select[Range@108, Part[Plus @@ DigitCount@ Divisors@ #, 2] > 0 &] (* _Michael De Vlieger_, Apr 20 2015 *) %o A257219 (Magma) [n: n in [1..1000] | [2] subset Setseq(Set(Sort(&cat[Intseq(d): d in Divisors(n)])))] %o A257219 (PARI) is(n)=!bittest(n,0)||setsearch(Set(digits(n)),2)||fordiv(n,d,setsearch(Set(digits(d)),2)&&return(1)) \\ _M. F. Hasler_, Apr 22 2015 %Y A257219 Cf. A037278, A176558, A243360, A256824. %K A257219 nonn,base %O A257219 1,1 %A A257219 _Jaroslav Krizek_, Apr 20 2015