A163656 - OEIS

A163656

Arithmetic mean of the n-th and (n+1)st twin prime member A001097.

4, 6, 9, 12, 15, 18, 24, 30, 36, 42, 51, 60, 66, 72, 87, 102, 105, 108, 123, 138, 144, 150, 165, 180, 186, 192, 195, 198, 213, 228, 234, 240, 255, 270, 276, 282, 297, 312, 330, 348, 384, 420, 426, 432, 447, 462, 492, 522, 546, 570, 585, 600, 609, 618, 630, 642

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

T. D. Noe, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = (A001097(n) + A001097(n+1))/2.

EXAMPLE

a(1) = 4 = (3+5)/2.

MATHEMATICA

t = Select[Prime[Range[500]], PrimeQ[# - 2] || PrimeQ[# + 2] &]; (Most[t] + Rest[t])/2 (* T. D. Noe, Aug 07 2012 *)

Mean/@Partition[Union[Flatten[Select[Partition[Prime[Range[200]], 2, 1], #[[2]]-#[[1]]==2&]]], 2, 1] (* Harvey P. Dale, Dec 07 2025 *)