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 A242739 #19 Sep 23 2022 15:36:38
%S A242739 4,14,74,77,111,141,177,411,417,447,471,717,771,1111,1114,1141,1147,
%T A242739 1174,1177,1411,1417,1441,1477,1711,1714,1717,1774,4117,4141,4171,
%U A242739 4174,4411,4414,4417,4471,4474,4711,4714,4717,4741,4747,4771,4777,7111,7114,7117,7141
%N A242739 Semiprimes having only straight digits.
%C A242739 A straight digit semiprime has only the straight digits, i.e., 1, 4 or 7.
%C A242739 Intersection of A001358 and A028373. - _Michel Marcus_, May 25 2014
%H A242739 K. D. Bajpai, <a href="/A242739/b242739.txt">Table of n, a(n) for n = 1..1727</a>
%e A242739 471 = 3 * 157 is semiprime and has only straight digits 4, 7 and 1. Hence it is in the sequence.
%e A242739 1147 = 31 * 37 is semiprime and has only straight digits 1, 1, 4 and 7. Hence it is in the sequence.
%t A242739 A242739 = {}; Do[a = PrimeOmega[n]; If [a == 2 && Intersection[IntegerDigits[n], {0, 2, 3, 5, 6, 8, 9}] == {}, AppendTo[A242739, n]], {n, 8000}]; A242739
%t A242739 Table[Select[FromDigits/@Tuples[{1,4,7},n],PrimeOmega[#]==2&],{n,4}]//Flatten (* _Harvey P. Dale_, Sep 23 2022 *)
%Y A242739 Cf. A001358, A028373, A079651, A108631, A108632.
%K A242739 nonn,base
%O A242739 1,1
%A A242739 _K. D. Bajpai_, May 21 2014