A072569 - OEIS

A072569

Odd interprimes.

9, 15, 21, 39, 45, 69, 81, 93, 99, 105, 111, 129, 165, 195, 205, 217, 225, 231, 279, 309, 315, 351, 363, 381, 393, 399, 405, 441, 453, 459, 465, 473, 483, 489, 495, 501, 515, 615, 625, 645, 667, 675, 687, 705, 723, 741, 747, 759, 765, 771, 803, 825, 855, 861

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

OFFSET

1,1

COMMENTS

The interprimes (A024675) are those integers that lie at the midpoint between consecutive odd primes.

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Eric Weisstein's World of Mathematics, Interprime

MATHEMATICA

a = Table[ Prime[n], {n, 2, 200}]; b = {}; Do[d = (a[[n + 1]] - a[[n]])/2; If[ OddQ[ a[[n]] + d], b = Append[b, a[[n]] + d]], {n, 1, 198}]; b

Select[Plus @@@ Partition[Table[Prime[n], {n, 2, 100}], 2, 1]/2, OddQ]

Select[Mean/@Partition[Prime[Range[2, 200]], 2, 1], OddQ] (* Harvey P. Dale, Jan 22 2019 *)