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A068859
a(1) = 3 = 1*3; a(n) = smallest multiple of a(n-1) which is of the form k(k+2).
2
3, 15, 120, 360, 5040, 201600, 256032000, 4064251968000, 1024126980000259968000, 29365589556381243259975904529351552000, 82421263677202543043706796882184010324019881962069201381742720000
OFFSET
1,1
LINKS
EXAMPLE
120 = 10*12 belongs to this sequence and 360 = 18*20 is the smallest such multiple of 120.
PROG
(Python)
from itertools import islice
from sympy import sqrt_mod_iter
def A068859_gen(): # generator of terms
a = 3
while True:
yield a
b = a+1
for d in sqrt_mod_iter(1, a):
if d==1 or d**2-1 == a:
d += a
if d < b:
b = d
a = b**2-1
A068859_list = list(islice(A068859_gen(), 11)) # Chai Wah Wu, May 05 2024
CROSSREFS
Sequence in context: A121422 A060639 A068052 * A006454 A225115 A303353
KEYWORD
nonn
AUTHOR
Amarnath Murthy, Mar 12 2002
EXTENSIONS
More terms from Sascha Kurz, Mar 23 2002
Edited by Don Reble, Sep 12 2003
STATUS
approved