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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
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
Sequence in context: A093121 A248048 A209298 * A088255 A192083 A068720
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.)