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A136349
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Numbers n of the form product( prime(i), i=1..k) such that n-1 is prime.
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9
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6, 30, 2310, 30030, 304250263527210, 23768741896345550770650537601358310, 19361386640700823163471425054312320082662897612571563761906962414215012369856637179096947335243680669607531475629148240284399976570
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Next term is too large to be included: see A006794. - M. F. Hasler, May 02 2008
This sequence is different from A121069 and A002110.
Compute the product of k consecutive sequences of prime factors 2,3,5,7, etc. where k=1,2,3,4,5, etc. When N is preceded by prime N-1 add N to the sequence.
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FORMULA
| a(n) = A057705(n) + 1 = A034386( A006794(n) ). - M. F. Hasler, May 02 2008
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EXAMPLE
| a(3)=30 where the prime factors are 2,3,5; since N-1=29, prime, N=30 is added to the sequence.
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MATHEMATICA
| Select[FoldList[Times, 1, Prime[Range[70]]], PrimeQ[#-1]&] [From Harvey P. Dale, Jan. 9, 2011]
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PROG
| (PARI) c=0; t=1; vector(7, n, until( ispseudoprime( -1+t*=prime(c++)), ); t)
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CROSSREFS
| Cf. A136350 A136351 A136352 A002110 A121069.
Sequence in context: A200894 A202861 A088256 * A119411 A036285 A101340
Adjacent sequences: A136346 A136347 A136348 * A136350 A136351 A136352
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KEYWORD
| nonn
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AUTHOR
| Enoch Haga (Enokh(AT)comcast.net), Dec 25 2007
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EXTENSIONS
| Edited by M. F. Hasler (www.univ-ag.fr/~mhasler), May 02 2008, May 30 2008
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