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 A075590 Smallest number with n distinct prime divisors which is the average of a twin prime pair. 6
 4, 6, 30, 420, 2310, 43890, 1138830, 17160990, 300690390, 15651726090, 239378649510, 12234189897930, 461282657605770, 19835154277048110, 693386350578511590, 37508276737897976010, 3338236629672919864890, 209580878166809177658630, 11465419967969569966774410 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS T. D. Noe, Table of n, a(n) for n = 1..50 EXAMPLE a(4) = 420 = 2^2*3*5*7, (419,421) is a twin prime pair. (210 = 2*3*5*7, 211 is prime but 209 is composite). a(8) = 17160990 = 2*3*5*7*11*17*19*23 and 17160989 = p[1100977], 17160991 = p[1100978]. MATHEMATICA t=Table[0, {10}]; Do[s=Length[FactorInteger[Prime[n]+1]]; If[PrimeQ[Prime[n]+2] && s<11 && t[[s]]==0, t[[s]]=Prime[n]+1], {n, 1, 1200000}]; t CROSSREFS Cf. A014574, A068525, A294730. Sequence in context: A093121 A248048 A209298 * A088255 A192083 A068720 Adjacent sequences: A075587 A075588 A075589 * A075591 A075592 A075593 KEYWORD nonn AUTHOR Amarnath Murthy, Sep 26 2002 EXTENSIONS More terms from Labos Elemer, Sep 27 2002 Corrected and extended by T. D. Noe, Nov 30 2004. a(9)-a(18) were found by testing all the numbers x with n distinct prime factors, x < 3 prime(n)# and both x-1 and x+1 prime. STATUS approved

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Last modified March 5 05:10 EST 2024. Contains 370537 sequences. (Running on oeis4.)