

A230290


a(n) = Sum_{i=1..n} d(24*i+1)  Sum_{i=1..n} d(6*i+1), where d(n) = A000005(n).


8



1, 2, 2, 1, 2, 4, 5, 4, 4, 4, 6, 7, 7, 5, 4, 10, 10, 10, 8, 9, 11, 10, 12, 10, 10, 13, 15, 14, 12, 14, 14, 14, 16, 16, 17, 17, 19, 21, 19, 20, 20, 18, 16, 16, 18, 24, 24, 23, 23, 21, 28, 28, 28, 24, 24, 26, 25, 27, 27, 28, 30, 30, 32, 28, 28, 30, 28, 30, 28, 29, 33, 39, 39, 37, 35, 39, 40, 38, 36, 36, 38
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OFFSET

1,2


COMMENTS

Every inequality in number theory of the form f(n) >= g(n) is a potential source of a sequence floor(f(n))ceiling(g(n)).
That sequence can be negative (e.g., floor(2/3)ceiling(1/3)=1), but the other 3 differences floor(f(n))floor(g(n)), ceiling(f(n))ceiling(g(n)), and ceiling(f(n))floor(g(n)) are nonnegative.  Jonathan Sondow, Oct 20 2013


LINKS

Robert Israel, Table of n, a(n) for n = 1..10000
Jorge Luis Cimadevilla Villacorta, Certain inequalities associated with the divisor function, Amer. Math. Monthly, 120 (2013), 832837. (Shows that a(n) >= 0.)


MAPLE

with(numtheory);
f:=proc(n, a, b, c, d) local i; add(tau(a*i+b), i=1..n)  add(tau(c*i+d), i=1..n); end;
[seq(f(n, 24, 1, 6, 1), n=1..120)];
# More efficient:
ListTools:PartialSums([seq(numtheory:tau(24*i+1)numtheory:tau(6*i+1), i=1..120)]); # Robert Israel, Jan 03 2020


PROG

(PARI) vector(100, n, sum(i=1, n, numdiv(24*i+1))  sum(i=1, n, numdiv(6*i+1))) \\ Michel Marcus, Oct 09 2014
(MAGMA) [&+[#Divisors(24*i+1):i in [1..n]]  &+[#Divisors(6*i+1):i in [1..n]]:n in [1..85]]; // Marius A. Burtea, Jan 03 2020


CROSSREFS

Cf. A000005, A230291, A230292, A230293, A230294, A230295, A230296.
Sequence in context: A143808 A294600 A247495 * A294783 A172021 A325182
Adjacent sequences: A230287 A230288 A230289 * A230291 A230292 A230293


KEYWORD

nonn


AUTHOR

N. J. A. Sloane, Oct 17 2013


STATUS

approved



