OFFSET
1,1
COMMENTS
LINKS
Chai Wah Wu, Table of n, a(n) for n = 1..10602
EXAMPLE
36 = 1*36 = 6*6. 45 = 1*45 = 3*15. 210 = 1*210 = 10*21. 315 = 3*105 = 15*21. 360 = 3*120 = 10*36. 630 = 1*630 = 3*210 = 6*105. 3780= 6*360 = 10 * 378 = 36*105.
MAPLE
A264961ct := proc(n)
local ct, d ;
ct := 0 ;
for d in numtheory[divisors](n) do
if d^2 > n then
return ct;
end if;
if isA000217(d) then
if isA000217(n/d) then
ct := ct+1 ;
end if;
end if;
end do:
return ct;
end proc:
for n from 1 to 30000 do
if A264961ct(n) > 1 then
printf("%d, ", n) ;
end if;
end do:
MATHEMATICA
lim = 10000; t = Accumulate[Range@lim]; f[n_] := Select[{#, n/#} & /@ Select[Divisors@ n, # <= Sqrt@ n && MemberQ[t, #] &], MemberQ[t, Last@ #] &]; Select[Range@ lim, Length@ f@ # == 2 &] (* Michael De Vlieger, Nov 29 2015 *)
PROG
(Python)
from __future__ import division
mmax = 10**3
tmax, A264961_dict = mmax*(mmax+1)//2, {}
ti = 0
for i in range(1, mmax+1):
ti += i
p = ti*i*(i-1)//2
for j in range(i, mmax+1):
p += ti*j
if p <= tmax:
else:
break
CROSSREFS
KEYWORD
nonn
AUTHOR
R. J. Mathar, Nov 29 2015
STATUS
approved