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A209637
Matula-numbers computed for rooted trees encoded by A071162 when interpreted in once-halved bit-tuple format.
5
1, 2, 3, 4, 5, 7, 6, 8, 11, 17, 13, 19, 10, 14, 12, 16, 31, 59, 41, 67, 29, 43, 37, 53, 22, 34, 26, 38, 20, 28, 24, 32, 127, 277, 179, 331, 109, 191, 157, 241, 79, 139, 101, 163, 71, 107, 89, 131, 62, 118, 82, 134, 58, 86, 74, 106, 44, 68, 52, 76, 40, 56, 48
OFFSET
0,2
COMMENTS
Sequence A209638 gives the same terms sorted into ascending order.
REFERENCES
Mueller, Szymanski, Knop and Trinajstic, A Comparison between the Matula Numbers and Bit-tuple Notation for Rooted Trees J. Chem. Inf. Comput. Sci. 1995, 35, pp. 211--213.
FORMULA
PROG
(Python)
from sympy import prime
from mpmath import log
def a054429(n): return 3*(2**int(log(n, 2))) - (n + 1)
def a209636(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
def a(n): return 1 if n==0 else a209636(a054429(n)) # Indranil Ghosh, May 26 2017
CROSSREFS
Sequence in context: A066937 A217266 A347539 * A347540 A120750 A265672
KEYWORD
nonn,easy
AUTHOR
Antti Karttunen, Mar 11 2012
STATUS
approved