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A338884
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The smallest number of bits which need to be appended to the binary representation of n to reach a prime greater than n.
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1
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1, 1, 1, 2, 1, 1, 2, 1, 1, 2, 1, 3, 2, 1, 1, 2, 2, 1, 2, 1, 1, 2, 1, 2, 2, 1, 2, 2, 1, 1, 2, 2, 1, 2, 1, 1, 2, 3, 1, 2, 1, 3, 2, 1, 2, 3, 2, 1, 2, 1, 1, 2, 1, 1, 2, 1, 2, 2, 2, 2, 3, 2, 1, 2, 1, 4, 2, 1, 1, 2, 3, 3, 2, 1, 1, 2, 2, 1, 2, 3, 1, 2, 1, 2, 3, 1, 2
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OFFSET
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1,4
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COMMENTS
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a(n) is also the distance from a node to its first prime-number descendant in a binary tree defined as: root = 1 and, for any node n, the left child = 2*n and right child = 2*n + 1. The number of primes among the nodes of depth m is equal to A036378(m) for m>=2.
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LINKS
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FORMULA
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PROG
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(Python)
from sympy import isprime
for n in range(1, 101):
a = 0
k = i = 1
while isprime(i) == 0:
a += 1
k = 2*k
for i in range(k*n + 1, k*n + k):
if isprime(i) == 1: break
print(a)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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