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 A133304 #15 Mar 14 2025 17:10:32
%S A133304 2,3,5,5,5,6,5,5,5,4,5,4,5,7,7,6,5,4,5,9,7,5,4,5,6,6,8,5,6,4,7,5,7,5,
%T A133304 5,7,4,4,6,7,6,7,8,5,8,7,6,5,7,7,6,7,4,5,8,7,8,8,7,6
%N A133304 Number of distinct prime factors of A101291.
%H A133304 Dario Alpern, <a href="https://www.alpertron.com.ar/ecm.htm">Factorization using the Elliptic Curve Method</a>.
%e A133304 The number of distinct prime factors of 45 is 2.
%e A133304 The number of distinct prime factors of 4905 is 3.
%e A133304 The number of distinct prime factors of 494550 is 5.
%p A133304 A101291 := proc(n) 99*100^n/200-9*10^n/20 ; end: A133304 := proc(n) nops(numtheory[factorset](A101291(n))) ; end: for n from 1 do printf("%d,\n",A133304(n)) ; od: # _R. J. Mathar_, Jul 08 2009
%t A133304 f[n_] := 10^n(10^n - 1)/2; Table[PrimeNu[f[n] - f[n - 1]], {n, 60}] (* _James C. McMahon_, Mar 14 2025 *)
%Y A133304 Cf. A101291.
%K A133304 nonn,base
%O A133304 1,1
%A A133304 _Parthasarathy Nambi_, Oct 18 2007
%E A133304 28 more terms from _R. J. Mathar_, Jul 08 2009
%E A133304 a(41)-a(60) from _James C. McMahon_, Mar 14 2025