This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A071259 #10 Feb 24 2018 16:20:37
%S A071259 3,4,6,8,10,12,15,17,19,23,25,29,31,33,36,39,43,44,48,51,53,56,59,62,
%T A071259 67,70,71,74,76,79,86,89,93,94,100,101,105,109,111,115,118,120,126,
%U A071259 128,130,132,138,145,148,149,152,156,158,163,167,170,174,176,179,182,184
%N A071259 Integer part of the arithmetic mean of the n-th prime p(n) and the n-th composite number C(n).
%H A071259 Harvey P. Dale, <a href="/A071259/b071259.txt">Table of n, a(n) for n = 1..2500</a>
%F A071259 Floor [ (p(n) + C(n))/2]
%F A071259 a(n)=Floor[[A000040(n)+A002808(n)]/2]; Prime[n]>a(n)>Composite[n]
%e A071259 a(7) = {p(7) + C(7)}/2 = (17 + 14)/2 = 15.
%e A071259 p(9) = 23, C(9) = 16, average = 19.5, a(9) = 19.
%t A071259 c[x_] := FixedPoint[x+PrimePi[ # ]+1&, x] Do[s=(Prime[n]+c[n])/2; If[IntegerQ[s], Print[s]], {n, 1, 256}]
%t A071259 IntegerPart[Mean[#]]&/@Module[{nn=100,cmps},cmps=Select[Range[nn], CompositeQ]; Thread[{cmps,Prime[Range[Length[cmps]]]}]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Feb 24 2018 *)
%Y A071259 Cf. A000040, A002808, A073432, A073433, A071260.
%K A071259 nonn
%O A071259 1,1
%A A071259 _Amarnath Murthy_, May 30 2002
%E A071259 More terms from _Labos Elemer_, Jul 31 2002