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 A050690 #26 Jul 28 2025 05:38:02
%S A050690 12,32,1152,11232,13122,14112,21312,111132,112112,3121152,11231232,
%T A050690 11354112,812122112,1251213312,2211121152,2211213312,5121114112,
%U A050690 26122125312,56321114112,62214111232,431711322112,3421411213312,11111212122112,11112113242112
%N A050690 Sum of digits of zero-absent composite a(n) equals number of prime factors.
%C A050690 10^11 < a(21) <= 431711322112. a(22) <= 3421411213312. - _Donovan Johnson_, May 30 2010
%C A050690 Do all terms end in 2, i.e., is each term = 2 mod 10? - _Harvey P. Dale_, May 26 2024
%e A050690 E.g., 21312 (no zero in the string) gives 2+1+3+1+2 = 9 prime factors, namely, 2*2*2*2*2*2*3*3*37.
%t A050690 t={}; Do[If[FreeQ[x=IntegerDigits[n],0]&&PrimeOmega[n]==Total[x],AppendTo[t,n]],{n,2,3220000,2}]; t (* _Jayanta Basu_, May 30 2013 *)
%Y A050690 Cf. A050689, A057531, A057532, A070274, A070275, A063737, A067077.
%K A050690 nonn,base,nice,hard
%O A050690 1,1
%A A050690 _Patrick De Geest_, Aug 15 1999
%E A050690 a(15)-a(20) from _Donovan Johnson_, May 30 2010
%E A050690 a(21)-a(22) confirmed by _Giovanni Resta_, Jun 02 2013
%E A050690 a(23)-a(24) from _Giovanni Resta_, Apr 23 2017