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 A263674 Double interprimes: a(n) = (q+r)/2 = (p+s)/2 with p
 9, 12, 15, 18, 30, 42, 60, 81, 102, 105, 108, 120, 144, 165, 186, 195, 228, 260, 270, 312, 363, 381, 399, 420, 426, 441, 462, 489, 495, 552, 570, 582, 600, 696, 705, 714, 765, 816, 825, 858, 870, 882, 897, 924, 987, 1026, 1050, 1056, 1092, 1113, 1167, 1230 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Values of p (lesser of consecutive primes) are in the sequence A022885. LINKS Eric Weisstein's World of Mathematics, Interprime EXAMPLE 600 is in this sequence because 593, 599, 601 and 607 are consecutive primes, and 600 = (599+601)/2 = (593+607)/2. MATHEMATICA (Prime@ # + Prime[# + 3])/2 & /@ Select[Range@ 240, (First@ # + Last@ #)/2 == (#[[2]] + #[[3]])/2 &@ Prime@ Range[#, # + 3] & (* Michael De Vlieger, Nov 18 2015 *) PROG (PARI) {forprime(q=3, 2000, p=precprime(q-1); r=nextprime(q+1); s=nextprime(r+1); m=(q+r)/2; if(m==(p+s)/2, print1(m, ", ")))} CROSSREFS Cf. A022885, A075190, A075277, A075296, A078443, A130178, A263675, A263676. Sequence in context: A102655 A308748 A120167 * A048699 A019468 A084799 Adjacent sequences:  A263671 A263672 A263673 * A263675 A263676 A263677 KEYWORD nonn AUTHOR Antonio Roldán, Oct 23 2015 STATUS approved

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Last modified October 22 00:52 EDT 2019. Contains 328315 sequences. (Running on oeis4.)