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A209638 Sequence A209636 (or A209637) sorted into ascending order. 5


%S 1,2,3,4,5,6,7,8,10,11,12,13,14,16,17,19,20,22,24,26,28,29,31,32,34,

%T 37,38,40,41,43,44,48,52,53,56,58,59,62,64,67,68,71,74,76,79,80,82,86,

%U 88,89,96,101,104,106,107,109,112,116,118,124,127,128,131,134

%N Sequence A209636 (or A209637) sorted into ascending order.

%C 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.

%H <a href="/index/Mat#matula">Index entries for sequences related to Matula-Goebel numbers</a>

%o (Python)

%o from sympy import prime

%o def a(n):

%o n = 2*n

%o m = 1

%o if n<2: return 1

%o while n>1:

%o if n%2==0:

%o n//=2

%o m*=2

%o else:

%o n=(n - 1)//2

%o m=prime(m)

%o return m

%o print(sorted([a(n) for n in range(101)])) # _Indranil Ghosh_, May 26 2017

%Y Sorted version of A209636 and A209637.

%Y Subset of A093641 and A122132.

%K nonn

%O 0,2

%A _Antti Karttunen_, Mar 11 2012

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Last modified June 13 22:16 EDT 2021. Contains 345016 sequences. (Running on oeis4.)