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 A079721 #16 Aug 26 2025 08:47:44
%S A079721 15,24,34,54,72,76,88,102,110,131,153,162,173,189,255,324,342,353,374,
%T A079721 545,705,721,736,741,747,756,765,838,922,939,947,960,969,977,987,1000,
%U A079721 1015,1026,1032,1047,1065,1080,1094,1100,1106,1130,1152,1167,1187
%N A079721 Interemirp sequence: average of emirp pairs, analogous to interprimes.
%H A079721 Michael De Vlieger, <a href="/A079721/b079721.txt">Table of n, a(n) for n = 1..10000</a>
%H A079721 Michael Joseph Halm, <a href="http://untilheaven.tripod.com/id112.htm">Sequences</a>
%F A079721 a(n) = (A006567(n) + A006567(n+1))/2 where A006567(n) is the n-th emirp.
%e A079721 a(1) = 15 because the first two emirps are 13 and 17 and (13 + 17)/2 = 15
%t A079721 Map[Apply[Total, {##}]/2 &, Partition[Select[Prime[Range[5, 196]], And[PrimeQ@ IntegerReverse[#], ! PalindromeQ[#] ] &], 2, 1]] (* _Michael De Vlieger_, Aug 26 2025 *)
%Y A079721 Cf. A006567, A024675.
%K A079721 nonn,base
%O A079721 1,1
%A A079721 _Michael Joseph Halm_, Feb 17 2003
%E A079721 a(4) corrected by _Sean A. Irvine_, Aug 25 2025