cp's OEIS Frontend

A188348 Distance between n and the next number with the same number of distinct prime factors.

%I A188348 #12 Jan 24 2020 12:13:55
%S A188348 1,1,1,2,4,1,1,2,2,2,2,3,1,3,1,2,2,4,1,1,2,2,2,2,2,2,5,2,12,1,5,1,1,1,
%T A188348 2,4,1,1,4,2,18,4,1,1,2,2,2,4,1,1,2,6,1,1,1,1,4,2,6,3,1,2,3,3,4,4,1,3,
%U A188348 8,2,2,6,1,1,1,3,6,2,2,2,3,6,6,1,1,1,3,8,12
%N A188348 Distance between n and the next number with the same number of distinct prime factors.
%H A188348 Robert Israel, <a href="/A188348/b188348.txt">Table of n, a(n) for n = 2..10000</a>
%F A188348 {min d>0: A001221(n+d) = A001221(n)}.
%p A188348 N:= 200: # to use numbers up to N
%p A188348 V:= Array(2..N, n -> nops(numtheory:-factorset(n))):
%p A188348 A:= Array(2..N):
%p A188348 for n from 2 to N do
%p A188348   v:= V[n];
%p A188348   if assigned(Last[v]) then
%p A188348      A[Last[v]]:= n-Last[v]
%p A188348   fi;
%p A188348   Last[v]:= n;
%p A188348 od:
%p A188348 m:= min(select(t -> A[t]=0, [$2..N]))-1:
%p A188348 seq(A[i],i=2..m); # _Robert Israel_, Jan 24 2020
%o A188348 (PARI) for(n=2, 100, f=omega(n); m=n+1; while(omega(m)!=f, m++); print1(m-n, ", ")) \\ _Colin Barker_, Jun 27 2014
%Y A188348 Cf. A001221, A178139.
%K A188348 nonn
%O A188348 2,4
%A A188348 _Juri-Stepan Gerasimov_, Mar 28 2011
%E A188348 Renamed, edited and checked by R. J. Mathar, Mar 28 2011.