A075065 a(1) = 1 and then alternately even and odd composite numbers matching the parity of the index.

1, 4, 9, 6, 15, 8, 21, 10, 25, 12, 27, 14, 33, 16, 35, 18, 39, 20, 45, 22, 49, 24, 51, 26, 55, 28, 57, 30, 63, 32, 65, 34, 69, 36, 75, 38, 77, 40, 81, 42, 85, 44, 87, 46, 91, 48, 93, 50, 95, 52, 99, 54, 105, 56, 111, 58, 115, 60, 117, 62, 119, 64, 121, 66

Offset

1,2

Links

Table of n, a(n) for n=1..64.

Mathematica

Module[{nn=150, comps, odds, evens, len}, comps=Complement[Range[nn], Prime[Range[ PrimePi[nn]]]]; odds=Select[ comps, OddQ]; evens=Select[comps, EvenQ]; len=Min[ Length[odds], Length[evens]]; Riffle[Take[odds, len], Take[evens, len]]] (* Harvey P. Dale, Feb 19 2013 *)

Crossrefs

Cf. A075066.

Sequence in context: A335306 A261023 A171095 * A141553 A095065 A061207

Adjacent sequences: A075062 A075063 A075064 * A075066 A075067 A075068

Keyword

easy,nonn

Author

Amarnath Murthy, Sep 08 2002

Extensions

More terms from Harvey P. Dale, Feb 19 2013

Status

approved