OFFSET
0,2
COMMENTS
Note that all powers of 7 are terms in A002473.
Polynomial of fourth order is sufficient for very accurate approximation of a(n).
LINKS
Zak Seidov, Table of n, a(n) for n = 0..200
FORMULA
a(n) ~ c * n^4, where c = log(7)^3/(24*log(2)*log(3)*log(5)) = 0.250503020417439... - Vaclav Kotesovec and Amiram Eldar, Sep 22 2024
EXAMPLE
MATHEMATICA
ss7 = {}; Do[m = 7^n; s = Sum[1 + Floor[Log[2, 7^(n - k)/5^i/3^j]], {k, 0, n}, {i, 0, Log[5, 7^(n - k)]}, {j, 0, Log[3, 7^(n - k)/5^i]}]; AppendTo[ss7, {n, s}], {n, 0, 50}]; ss7
CROSSREFS
KEYWORD
nonn
AUTHOR
Zak Seidov, Nov 18 2013
STATUS
approved