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Numbers k such that omega(k+1) = 2*omega(k), where omega is the number of distinct prime factors.
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%I #16 Apr 29 2023 00:07:48

%S 5,9,11,13,17,19,23,25,27,32,37,43,47,49,53,61,64,67,71,73,79,81,97,

%T 103,107,121,128,151,157,163,191,193,199,209,211,223,241,243,271,277,

%U 283,313,329,331,337,343,361,367,383,397,421,431,457,463,487,499,512

%N Numbers k such that omega(k+1) = 2*omega(k), where omega is the number of distinct prime factors.

%H Harry J. Smith, <a href="/A063479/b063479.txt">Table of n, a(n) for n = 1..1000</a>

%e omega(209)=2, omega(209+1)=2*2, so 209 is a term of the sequence.

%o (PARI) j=[]; for(n=1,700, if(omega(n+1)==2*omega(n),j=concat(j,n))); j

%o (PARI) { n=0; for (m=1, 10^9, if (omega(m + 1) == 2*omega(m), write("b063479.txt", n++, " ", m); if (n==1000, break)) ) } \\ _Harry J. Smith_, Aug 23 2009

%K easy,nonn

%O 1,1

%A _Jason Earls_, Jul 28 2001