A155108 - OEIS

%I #11 Feb 10 2019 23:05:07

%S 2,3,5,7,11,13,19,29,31,37,41,43,47,59,67,71,79,83,89,101,103,107,109,

%T 113,127,137,139,149,151,157,163,179,181,197,199,211,233,239,241,251,

%U 257,263,269,271,277,281,293,307,311,331,337,347,349,353,359,373,389

%N Primes k such that the k-th composite is even.

%H Muniru A Asiru, <a href="/A155108/b155108.txt">Table of n, a(n) for n = 1..20000</a>

%e 2 is a term because composite(2) = 6 (even);

%e 3 is a term because composite(3) = 8 (even);

%e 5 is a term because composite(5) = 10 (even);

%e 7 is a term because composite(7) = 14 (even);

%e 11 is a term because composite(11) = 20 (even).

%o (GAP) A:=Filtered([2..500],n->not IsPrime(n));;

%o a:=Filtered(Filtered([1..Length(A)],IsPrime),i->IsEvenInt(A[i])); # _Muniru A Asiru_, Feb 10 2019

%Y Cf. A000040, A002808.

%K nonn

%O 1,1

%A _Juri-Stepan Gerasimov_, Jan 20 2009

%E Corrected (105 replaced by 107, 239 and 263 inserted) by _R. J. Mathar_, May 10 2010