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A075590
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Smallest number with n prime divisors which is the average of a twin prime pair.
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2
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4, 6, 30, 420, 2310, 43890, 1138830, 17160990, 300690390, 15651726090, 239378649510, 12234189897930, 461282657605770, 19835154277048110, 693386350578511590, 37508276737897976010, 3338236629672919864890
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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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].
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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
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CROSSREFS
| Sequence in context: A090530 A154667 A093121 * A088255 A192083 A068720
Adjacent sequences: A075587 A075588 A075589 * A075591 A075592 A075593
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KEYWORD
| nonn
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AUTHOR
| Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Sep 26 2002
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EXTENSIONS
| More terms from Labos E. (labos(AT)ana.sote.hu), Sep 27 2002
Corrected and extended by T. D. Noe (noe(AT)sspectra.com), 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.
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