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Twice composite numbers.
0

%I #16 Feb 25 2017 08:10:57

%S 8,12,16,18,20,24,28,30,32,36,40,42,44,48,50,52,54,56,60,64,66,68,70,

%T 72,76,78,80,84,88,90,92,96,98,100,102,104,108,110,112,114,116,120,

%U 124,126,128,130,132,136,138,140,144,148,150,152,154,156,160,162,164,168,170,172,174

%N Twice composite numbers.

%C Even numbers greater than 2 that do not appear in A001747.

%F a(n) = 2*A002808(n). - _R. J. Mathar_, Feb 23 2017

%F a(n) = A139270(n+1). - _R. J. Mathar_, Feb 25 2017

%o (PARI) is(n)=n%2==0 && n>6 && !isprime(n/2) \\ _Charles R Greathouse IV_, Feb 21 2017

%Y Cf. A001747, A139270, A176100.

%K nonn,easy

%O 1,1

%A _Alessandro Polcini_, Feb 20 2017