OFFSET
0,2
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 0..10000
FORMULA
a(n) ~ kn^2 + O(n) with k = log(7)/log(2) - log(7)^2/log(2)^2. - Charles R Greathouse IV, Jun 28 2011
PROG
(PARI) a(n)=my(N=7<<n); sum(k=0, log(N)\log(7)-1, #binary(N\=7)) \\ Charles R Greathouse IV, Jun 28 2011
(PARI) a(n)=my(N=1); n+1+sum(i=1, n, logint(N<<=1, 7)); \\ Charles R Greathouse IV, Jan 11 2018
(PARI) first(n)=my(s, N=1/2); vector(n+1, i, s+=logint(N<<=1, 7)+1) \\ Charles R Greathouse IV, Jan 11 2018
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
EXTENSIONS
An incorrect g.f. was deleted by N. J. A. Sloane, Sep 16 2009
STATUS
approved