OFFSET
0,2
COMMENTS
These are Matula-numbers (see A061773) for the rooted trees where no vertices with more than one non-leaf branch ever occur. In other words, natural numbers which are either some power of 2, or of the form 2^k * p_i, where k >= 0, and p_i is the i-th prime (A000040(i)), with i being one of the terms of this sequence.
PROG
(Python)
from sympy import prime
def a(n):
n = 2*n
m = 1
if n<2: return 1
while n>1:
if n%2==0:
n//=2
m*=2
else:
n=(n - 1)//2
m=prime(m)
return m
print(sorted([a(n) for n in range(101)])) # Indranil Ghosh, May 26 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Mar 11 2012
STATUS
approved