A079721 Interemirp sequence: average of emirp pairs, analogous to interprimes.

15, 24, 34, 54, 72, 76, 88, 102, 110, 131, 153, 162, 173, 189, 255, 324, 342, 353, 374, 545, 705, 721, 736, 741, 747, 756, 765, 838, 922, 939, 947, 960, 969, 977, 987, 1000, 1015, 1026, 1032, 1047, 1065, 1080, 1094, 1100, 1106, 1130, 1152, 1167, 1187

Offset: 1

Author

Michael Joseph Halm, Feb 17 2003

Keywords

• nonn
• base

Examples

			a(1) = 15 because the first two emirps are 13 and 17 and (13 + 17)/2 = 15
		

Links

• Michael De Vlieger, Table of n, a(n) for n = 1..10000
• Michael Joseph Halm, Sequences

Crossrefs

Cf. A006567, A024675.

Programs

Mathematica

Map[Apply[Total, {##}]/2 &, Partition[Select[Prime[Range[5, 196]], And[PrimeQ@ IntegerReverse[#], ! PalindromeQ[#] ] &], 2, 1]] (* Michael De Vlieger, Aug 26 2025 *)

Formula

a(n) = (A006567(n) + A006567(n+1))/2 where A006567(n) is the n-th emirp.

Extensions

a(4) corrected by Sean A. Irvine, Aug 25 2025