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A072569 Odd interprimes. 24
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 *)

CROSSREFS

Odd members of A024675. Sequence is union of A072572 and A072573.

Cf. A024675, A072568.

Sequence in context: A020192 A241809 A063174 * A072572 A029708 A125215

Adjacent sequences:  A072566 A072567 A072568 * A072570 A072571 A072572

KEYWORD

nonn

AUTHOR

Marco Matosic, Jun 24 2002

EXTENSIONS

Edited by N. J. A. Sloane and Robert G. Wilson v, Jun 27 2002

STATUS

approved

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Last modified October 16 05:35 EDT 2019. Contains 328044 sequences. (Running on oeis4.)