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 A380758 #22 Mar 04 2025 16:19:31
%S A380758 39,69,117,119,129,159,207,219,249,259,299,309,329,339,341,351,387,
%T A380758 451,469,477,489,507,519,551,559,579,621,629,657,669,671,679,689,699,
%U A380758 747,749,781,789,799,833,849,879,889,897,927,939,949,959,989,1017,1053,1059
%N A380758 Numbers which are not prime powers and their prime factors share a last digit in base 10.
%C A380758 Also called the one-sided numbers.
%C A380758 They can end only in either 1, 3, 7 or 9.
%H A380758 Alois P. Heinz, <a href="/A380758/b380758.txt">Table of n, a(n) for n = 1..10000</a>
%H A380758 VOS 2025 Math Region stage, <a href="https://vos.olimpiada.ru/upload/files/Arhive_tasks/2024-25/reg/math/tasks-math-10-day2-reg-24-25.pdf">Problem 10.9</a> (in Russian).
%e A380758 39 = 3*13.
%p A380758 q:= n-> (l-> nops(l)>1 and nops({map(i-> irem(i[1], 10), l)[]})=1)(ifactors(n)[2]):
%p A380758 select(q, [$1..2000])[]; # _Alois P. Heinz_, Feb 18 2025
%t A380758 Sort[Times@@@Cases[Subsets[Prime[Range[100]],{2}],_?(Mod[#[[1]]-#[[2]],10]==0&)]][[;;100]] (* _Shenghui Yang_, Feb 18 2025 *)
%o A380758 (PARI) isok(k) = my(f=factor(k)); (#f~ != 1) && (#Set(vector(#f~, i, f[i,1] % 10)) == 1); \\ _Michel Marcus_, Feb 18 2025
%o A380758 (Python)
%o A380758 from sympy import factorint
%o A380758 def ok(n): return len(f:=factorint(n)) > 1 and len(set(p%10 for p in f)) == 1
%o A380758 print([k for k in range(1, 1060) if ok(k)]) # _Michael S. Branicky_, Feb 18 2025
%Y A380758 Cf. A004615.
%K A380758 nonn,base
%O A380758 1,1
%A A380758 _Yaroslav Deryavko_, Feb 01 2025