OFFSET
1,2
COMMENTS
This sequence has properties related to primes. For instance: a(n+1)/a(n)-1 consists of 1's or primes only. Any prime p>=3 divides a(n) for the first time when n=p*w(p)-1 where w(p) is the least positive integer such that p*w(p)-1 is prime.
See A135506 for more comments and references.
LINKS
T. D. Noe, Table of n, a(n) for n=1..100
MATHEMATICA
a[1] = 1; a[n_] := a[n] = a[n-1] + LCM[a[n-1], n]; Table[a[n], {n, 1, 24}] (* Jean-François Alcover, Dec 16 2011 *)
RecurrenceTable[{a[1]==1, a[n]==a[n-1]+LCM[a[n-1], n]}, a, {n, 30}] (* Harvey P. Dale, Mar 03 2013 *)
PROG
(PARI) x1=1; for(n=2, 40, x2=x1+lcm(x1, n); t=x1; x1=x2; print1(x2, ", "))
(Haskell)
a135504 n = a135504_list !! (n-1)
a135504_list = 1 : zipWith (+)
a135504_list (zipWith lcm a135504_list [2..])
-- Reinhard Zumkeller, Oct 03 2012
(Python)
from sympy import lcm
l=[0, 1]
for n in range(2, 101):
x=l[n - 1]
l.append(x + lcm(x, n))
print(l) # Indranil Ghosh, Jun 27 2017
CROSSREFS
KEYWORD
nonn,nice
AUTHOR
Benoit Cloitre, Feb 09 2008, Feb 10 2008
STATUS
approved