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A072569 Odd interprimes. 23

%I

%S 9,15,21,39,45,69,81,93,99,105,111,129,165,195,205,217,225,231,279,

%T 309,315,351,363,381,393,399,405,441,453,459,465,473,483,489,495,501,

%U 515,615,625,645,667,675,687,705,723,741,747,759,765,771,803,825,855,861

%N Odd interprimes.

%C The interprimes (A024675) are those integers that lie at the mid-point between consecutive odd primes.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Interprime.html">Interprime</a>

%F (P_n+1 - P_n)/2 is odd.

%t 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

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

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

%Y Cf. A024675, A072568.

%K nonn

%O 1,1

%A _Marco Matosic_, Jun 24 2002

%E Edited by _N. J. A. Sloane_ and _Robert G. Wilson v_, Jun 27 2002

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Last modified December 19 01:34 EST 2014. Contains 252175 sequences.