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A079482 Smallest number k such that k and k+1 have n and n+1 distinct prime divisors. 1

%I

%S 1,5,65,1364,40754,1774409,58524465,5327923964,555409903685,

%T 70367042561529,5819629108725509,567969628457303709

%N Smallest number k such that k and k+1 have n and n+1 distinct prime divisors.

%e a(3) = 1364 because 1364 has 3 and 1365 has 4 distinct prime divisors.

%t a[n_] := Module[{k = 1}, While[PrimeNu[k] != n || PrimeNu[k + 1] != n + 1, k++]; k]; Array[a, 10, 0] (* _Amiram Eldar_, Dec 03 2018 *)

%o (PARI) for(n=1,10,k=1; while(omega(k)!=n || omega(k+1)!=n+1,k++); print1(k","))

%Y Cf. A001221.

%K more,nonn

%O 0,2

%A _Jason Earls_, Jan 16 2003

%E a(6) from _Ryan Propper_, Jul 21 2006

%E a(7)-a(8) from _Donovan Johnson_, Apr 05 2008

%E a(9)-a(11) from _Donovan Johnson_, Feb 04 2009

%E a(0)=1 preprended by _Rémy Sigrist_, Dec 03 2018

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Last modified February 20 08:44 EST 2019. Contains 320325 sequences. (Running on oeis4.)