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A062974 Numbers k such that omega(k+1) < 2*omega(k), where omega(k) is the number of distinct prime divisors of k.

%I A062974 #14 Apr 15 2023 23:31:57
%S A062974 2,3,4,6,7,8,10,12,14,15,16,18,20,21,22,24,26,28,30,31,33,34,35,36,38,
%T A062974 39,40,42,44,45,46,48,50,51,52,54,55,56,57,58,60,62,63,65,66,68,69,70,
%U A062974 72,74,75,76,77,78,80,82,84,85,86,87,88,90,91,92,93,94,95,96,98,99,100
%N A062974 Numbers k such that omega(k+1) < 2*omega(k), where omega(k) is the number of distinct prime divisors of k.
%C A062974 A001221(a(n)+1) < 2*A001221(a(n)).
%H A062974 Reinhard Zumkeller, <a href="/A062974/b062974.txt">Table of n, a(n) for n = 1..10000</a>
%o A062974 (PARI) j=[]; for(n=1,200, if(omega(n+1)<2*omega(n),j=concat(j,n))); j
%o A062974 (Haskell)
%o A062974 import Data.List (findIndices)
%o A062974 a062974 n = a062974_list !! (n-1)
%o A062974 a062974_list = map (+ 1) $ findIndices (< 0) $
%o A062974    zipWith (-) (tail a001221_list) $ map (* 2) a001221_list
%o A062974 -- _Reinhard Zumkeller_, Jan 22 2013
%Y A062974 Cf. A006049 (subsequence).
%K A062974 nonn
%O A062974 1,1
%A A062974 _Jason Earls_, Jul 26 2001