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A086247 Differences of successive 7-smooth numbers. 3
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 (list; graph; refs; listen; history; text; internal format)
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-Fran├žois Alcover, Oct 17 2021 *)

CROSSREFS

Cf. A002473, A061987, A085153.

Sequence in context: A194884 A078401 A271381 * A116452 A219966 A103958

Adjacent sequences:  A086244 A086245 A086246 * A086248 A086249 A086250

KEYWORD

nonn,look

AUTHOR

Reinhard Zumkeller, Jul 13 2003

STATUS

approved

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Last modified September 28 04:28 EDT 2022. Contains 357063 sequences. (Running on oeis4.)