A204219 Primes whose binary reversal is not prime.

2, 19, 59, 79, 89, 103, 109, 137, 139, 149, 157, 179, 191, 211, 239, 241, 271, 281, 293, 311, 317, 347, 367, 379, 389, 397, 401, 419, 439, 457, 467, 499, 523, 541, 547, 557, 563, 569, 587, 593, 607, 613, 641, 647, 659, 673, 719, 733, 743, 751, 761, 769, 787, 809, 811, 829, 859, 863, 877, 887, 919, 929, 971, 977, 983, 991, 997

Offset

1,1

Links

Table of n, a(n) for n=1..67.

Mathematica

a = {}; For[n = 1, n <= 1000, n++, If[PrimeQ[n], {d = Reverse[ IntegerDigits[n, 2]]; If[!PrimeQ[FromDigits[d, 2]], AppendTo[a, n]]}]]; a (* Hasler *)
Select[Prime[Range[170]], Not[PrimeQ[FromDigits[Reverse[IntegerDigits[#, 2]], 2]]] &] (* Alonso del Arte, Jan 13 2012 *)

Prog

(PARI) forprime(p=1, 1e3, if(!isprime(sum(i=1, #b=binary(p), b[i]<<i)\2), print1(p", ")))
(PARI) isok(k) = isprime(k) && !isprime(fromdigits(Vecrev(binary(k)), 2)); \\ Michel Marcus, Feb 19 2021
(Python)
from sympy import isprime, primerange
def ok(p): return not isprime(int(bin(p)[:1:-1], 2))
def aupto(lim): return [p for p in primerange(2, lim+1) if ok(p)]
print(aupto(1000)) # Michael S. Branicky, Feb 19 2021

Crossrefs

Complement of A074832 in A000040.

Cf. A076056, the base 10 equivalent.

Sequence in context: A215392 A340558 A140544 * A042149 A218547 A365494

Adjacent sequences: A204216 A204217 A204218 * A204220 A204221 A204222

Keyword

nonn,base

Author

M. F. Hasler, Jan 13 2012

Status

approved