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 A115961 a(n)=least number having exactly n distinct prime factors, the largest of which is greater than or equal to sqrt(a(n)). 5
 2, 6, 42, 930, 44310, 5338410, 902311410, 260630159790, 94084209188970, 49770436899273090, 41856930884959119930, 40224510201386387907030, 55067354465876062759959510, 92568222856398333359120816010 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS FORMULA a(n)=y*(smallest prime that is larger than y), where y is the product of first n-1 consecutive primes. a(n) = (n-1)# * NextPrime((n-1)#). a(n) = A002110(n-1) * NextPrime(A002110(n-1)). E.g. a(15) = 14# * 13082761331670077 = (2 * 3 * 5 * 7 * 11 * 13 * 17 * 19 * 23 * 29 * 31 * 37 * 41 * 43) + 13082761331670077, since 13082761331670077 = 14# + 47 is the least prime > 14#. - Jonathan Vos Post, Feb 13 2006 EXAMPLE a(3)=42; indeed, 42=2*3*7, 7>sqrt(42) and 2*3*5 does not qualify because 5product(ithprime(j), j=1..n-1)*nextprime(product(ithprime(j), j=1..n-1)): seq(a(n), n=1..16); CROSSREFS Cf. A115956, A115957, A115958, A115959, A115960. Cf. A002110. Sequence in context: A276453 A152479 A250309 * A123137 A014117 A242927 Adjacent sequences:  A115958 A115959 A115960 * A115962 A115963 A115964 KEYWORD nonn AUTHOR Emeric Deutsch, Feb 02 2006 STATUS approved

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Last modified December 5 10:45 EST 2019. Contains 329751 sequences. (Running on oeis4.)