A129767 - OEIS

%I #14 May 20 2023 06:29:58

%S 2,4,3,6,5,9,7,10,11,14,13,15,17,21,19,22,23,25,29,26,31,33,37,34,41,

%T 35,43,38,47,39,53,46,59,49,61,51,67,55,71,57,73,58,79,62,83,65,89,69,

%U 97,74,101,77,103,82,107,85,109,86,113,87,127,91,131,93,137,94,139,95,149

%N Interleaved primes and semiprimes.

%H Alois P. Heinz, <a href="/A129767/b129767.txt">Table of n, a(n) for n = 1..10000</a> (first 1000 terms from Harvey P. Dale)

%F a(2*n-1) = A000040(n), a(2*n) = A001358(n).

%t Module[{nn=200,pr,sp,len},pr=Prime[Range[PrimePi[nn]]];sp=Select[Range[ nn],PrimeOmega[#]==2&];len=Min[Length[pr],Length[sp]];Thread[{Take[ pr,len],Take[ sp,len]}]]//Flatten (* _Harvey P. Dale_, Jun 02 2020 *)

%Y Cf. A000040, A001358, A037143.

%K easy,less,nonn

%O 1,1

%A _Jonathan Vos Post_, Jun 02 2007