A086247 Differences of successive 7-smooth numbers.

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, 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, 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

Offset

1,10

Comments

A002473(n) is a term of A085153 iff a(n)=1.

Links

David A. Corneth, Table of n, a(n) for n = 1..10000

Eric Weisstein's World of Mathematics, Smooth Number

Formula

a(n) = A002473(n+1) - A002473(n).

Example

a(23) = 3 as A002473(23 + 1) - A002473(23) = 35 - 32 = 3. - David A. Corneth, Mar 31 2021

Mathematica

smooth7Q[n_] := n == Times@@({2, 3, 5, 7}^IntegerExponent[n, {2, 3, 5, 7}]);
Select[Range[1000], smooth7Q] // Differences (* Jean-François Alcover, Oct 17 2021 *)

Crossrefs

Cf. A002473, A061987, A085153.

Sequence in context: A078401 A372673 A271381 * A116452 A219966 A103958

Adjacent sequences: A086244 A086245 A086246 * A086248 A086249 A086250

Keyword

nonn,look

Author

Reinhard Zumkeller, Jul 13 2003

Status

approved