A161540 - OEIS

%I #7 Jul 07 2024 17:00:57

%S 5,11,13,23,31,67,73,97,107,109,113,137,139,157,163,167,197,199,211,

%T 233,239,251,257,269,271,293,307,311,313,331,337,347,353,359,367,373,

%U 401,409,449,457,479,487,491,503,541,547,569,571,577,587,593,607,613,617

%N Primes which are the sum of a smaller n and its composite(n) subscript. A002808 + a(n) (= prime)

%C 5 = composite(1)+1 = 4+1 ; 11 = composite(3)+3 = 8+3

%H Harvey P. Dale, <a href="/A161540/b161540.txt">Table of n, a(n) for n = 1..1000</a>

%t Module[{nn=400,cmps,len},cmps=Select[Range[nn],CompositeQ];len=Length[cmps];Select[ Total/@ Thread[{Range[len],cmps}],PrimeQ]] (* _Harvey P. Dale_, Jul 07 2024 *)

%Y A002808

%K nonn

%O 1,1

%A _Claudio Meller_, Jun 13 2009