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A361687
The number of divisors of 2*n^2 which are <=n.
1
1, 2, 3, 3, 3, 5, 3, 4, 5, 6, 3, 8, 3, 6, 8, 5, 3, 9, 3, 8, 9, 6, 3, 11, 5, 6, 7, 8, 3, 16, 3, 6, 9, 6, 8, 14, 3, 6, 9, 11, 3, 16, 3, 9, 13, 6, 3, 14, 5, 10, 9, 9, 3, 13, 9, 11, 9, 6, 3, 24, 3, 6, 14, 7, 9, 16, 3, 9, 9, 17, 3, 18, 3, 6, 14, 9, 8, 17, 3, 14, 9, 6, 3, 24, 9, 6, 9, 11
OFFSET
1,2
EXAMPLE
a(15)=8 because the divisors of 2*15^2=450 which are <=15 are 1, 2, 3, 5, 6, 9, 10 and 15.
MAPLE
A361687 := proc(n)
local a, d;
a := 0 ;
for d in numtheory[divisors](2*n^2) do
if d <= n then
a := a+1 ;
end if;
end do:
a ;
end proc:
seq(A361687(n), n=1..120) ;
PROG
(PARI) a(n) = sumdiv(2*n^2, d, d <= n); \\ Michel Marcus, Mar 21 2023
CROSSREFS
Cf. A361689.
Sequence in context: A103359 A020481 A066660 * A057957 A359507 A366660
KEYWORD
nonn
AUTHOR
R. J. Mathar, Mar 20 2023
STATUS
approved