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 A071852 #29 Sep 03 2022 18:46:32 %S A071852 1,5,14,18,30,42,99,114,78,90,175,150,324,210,315,234,270,585,405,765, %T A071852 390,450,510,1150,690,630,930,858,810,1155,966,1386 %N A071852 Smallest k such that 2^k + 1 has exactly n distinct prime factors. %C A071852 a(33) > 1500; a(34) = 1365; a(35) = 1350; a(38) = 1170; a(41) = 1530. - _Max Alekseyev_, Oct 14 2012 %C A071852 a(33) <= 1782; a(36) <= 1710; a(42) <= 2142; a(43) <= 2394; a(44) <= 1890; a(45) <= 2310; a(46) <= 2070. - _Jon E. Schoenfield_, Sep 03 2022 %F A071852 a(n) = min (k : A046799(k) = n ). %t A071852 For[n = 1, n < 15, n++, k := 1; While[Not[Length[FactorInteger[2^k + 1]] == n], k++ ]; Print[k]] (* _Stefan Steinerberger_, Apr 09 2006 *) %o A071852 (PARI) for(n=1,10,s=1; while(abs(omega(2^s+1)-n)>0,s++); print1(s,",")) %Y A071852 Cf. A046799. %K A071852 nonn,more %O A071852 1,2 %A A071852 _Benoit Cloitre_, Jun 09 2002 %E A071852 175 and 150 from _Erich Friedman_, Aug 08 2005 %E A071852 a(13)-a(23) from _Donovan Johnson_, Apr 22 2008 %E A071852 a(24)-a(32) from _Max Alekseyev_, Oct 14 2012