|
| |
|
|
A074831
|
|
Number of binary reversal primes less than 10^n.
|
|
0
|
|
|
|
3, 20, 101, 508, 3053, 20053, 141772, 1045600, 8038954, 63830588, 518935134, 4311185894
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
1,1
|
|
|
COMMENTS
|
MathPages counts 1 as being a binary reversal prime whereas the title would exclude it, therefore their count exceeds this count by one.
|
|
|
LINKS
|
Table of n, a(n) for n=1..12.
MathPages, Reflective and Cyclic Sets of Primes
|
|
|
MATHEMATICA
|
f[n_] := FromDigits[Reverse[IntegerDigits[n, 2]], 2]; NextPrim[n_] := Block[{k = n + 1}, While[ ! PrimeQ[k], k++ ]; k]; c = 0; k = 1; Do[ While[k = NextPrim[k]; k < 10^n, If[ PrimeQ[ f[k]], c++ ]]; k--; Print[c], {n, 16}]
|
|
|
PROG
|
(Python)
from sympy import isprime, primerange
def is_bin_rev_prime(n): return isprime(int(bin(n)[2:][::-1], 2))
def a(n): return sum(is_bin_rev_prime(p) for p in primerange(1, 10**n))
print([a(n) for n in range(1, 7)]) # Michael S. Branicky, Mar 20 2021
|
|
|
CROSSREFS
|
Sequence in context: A305203 A246150 A000948 * A203357 A304494 A000917
Adjacent sequences: A074828 A074829 A074830 * A074832 A074833 A074834
|
|
|
KEYWORD
|
nonn,base,hard,more
|
|
|
AUTHOR
|
Robert G. Wilson v, Sep 09 2002
|
|
|
EXTENSIONS
|
a(10)-a(11) from Chai Wah Wu, Oct 09 2018
a(12) from Chai Wah Wu, Oct 10 2018
|
|
|
STATUS
|
approved
|
| |
|
|
