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A219955 Numbers that cannot be represented as 2*p + 3*q, where p and q are prime. 7

%I #18 Dec 05 2012 17:07:46

%S 1,2,3,4,5,6,7,8,9,11,14,17,18,22,24,26,30,33,34,36,38,42,46,48,50,51,

%T 54,56,58,60,62,66,69,70,72,74,76,78,81,82,84,86,87,90,94,96,98,102,

%U 104,105,106,108,110,111,114,116,118,120,122,123,126,130,132

%N Numbers that cannot be represented as 2*p + 3*q, where p and q are prime.

%C Numbers not in A079026.

%H Zak Seidov, <a href="/A219955/b219955.txt">Table of n, a(n) for n = 1..1000</a>

%F a(n) < 1.5n + O(n/log n). - _Charles R Greathouse IV_, Dec 04 2012

%t mx = 200; Complement[Range[mx], Flatten@Table[2 Prime[i] + 3 Prime[k], {k, PrimePi[(mx - 4)/3]}, {i, PrimePi[(mx - 3 Prime[k])/2]}]] (* _Zak Seidov_, Dec 04 2012 *)

%o (PARI) list(lim)=my(v=vectorsmall(lim\1),u=List());forprime(p=2,lim\2, forprime(q=2, (lim-2*p)\3, v[2*p+3*q]=1)); for(i=1, #v, if(!v[i], listput(u,i)));Vec(u) \\ _Charles R Greathouse IV_, Dec 04 2012

%Y Cf. A079026.

%K nonn

%O 1,2

%A _Zak Seidov_, Dec 02 2012

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Last modified April 19 15:34 EDT 2024. Contains 371794 sequences. (Running on oeis4.)