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A086247 Differences of successive 7-smooth numbers.

%I A086247 #14 Feb 16 2025 08:32:50
%S A086247 1,1,1,1,1,1,1,1,1,2,2,1,1,2,2,1,3,1,2,1,2,2,3,1,4,2,3,3,1,1,4,2,4,3,
%T A086247 1,6,2,3,5,1,3,6,6,2,2,5,3,4,8,5,1,2,7,5,4,3,3,10,2,6,7,5,9,3,4,4,10,
%U A086247 6,8,1,15,3,2,5,2,4,14,10,8,6,6,15,5,4,12,7,7,10,15,3,6,8,8,5,15,12
%N A086247 Differences of successive 7-smooth numbers.
%C A086247 A002473(n) is a term of A085153 iff a(n)=1.
%H A086247 David A. Corneth, <a href="/A086247/b086247.txt">Table of n, a(n) for n = 1..10000</a>
%H A086247 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/SmoothNumber.html">Smooth Number</a>
%F A086247 a(n) = A002473(n+1) - A002473(n).
%e A086247 a(23) = 3 as A002473(23 + 1) - A002473(23) = 35 - 32 = 3. - _David A. Corneth_, Mar 31 2021
%t A086247 smooth7Q[n_] := n == Times@@({2, 3, 5, 7}^IntegerExponent[n, {2, 3, 5, 7}]);
%t A086247 Select[Range[1000], smooth7Q] // Differences (* _Jean-François Alcover_, Oct 17 2021 *)
%Y A086247 Cf. A002473, A061987, A085153.
%K A086247 nonn,look
%O A086247 1,10
%A A086247 _Reinhard Zumkeller_, Jul 13 2003