The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A238090 Primes whose hexadecimal representation contains only consonants. 2

%I

%S 11,13,191,223,251,3019,3023,3037,3067,3259,3323,3517,3533,3547,3581,

%T 3583,4027,4091,4093,48079,48091,48383,48571,48589,49103,49117,52189,

%U 52223,52667,52733,53197,56267,56269,56509,56527,56543,56767,56779,56783,56827,64717,64763,769019,769231,769243,769247,769469,769487

%N Primes whose hexadecimal representation contains only consonants.

%C Primes whose hexadecimal representation contains only the "digits" B, C, D and F.

%C There are no primes whose hexadecimal representation contains only the vowels A and E (for these would be even numbers greater than 2).

%H Michael S. Branicky, <a href="/A238090/b238090.txt">Table of n, a(n) for n = 1..21472</a> (all terms with <= 9 hexadecimal digits; terms 1..166 from N. J. A. Sloane)

%e The first few terms and their hexadecimal representations (written with least significant "digit" on the left) are:

%e 11, [B]

%e 13, [D]

%e 191, [F, B]

%e 223, [F, D]

%e 251, [B, F]

%e 3019, [B, C, B]

%e 3023, [F, C, B]

%e 3037, [D, D, B]

%e 3067, [B, F, B]

%e 3259, [B, B, C]

%e 3323, [B, F, C]

%e ...

%o (Python)

%o from sympy import isprime, primerange

%o def ok(p): return set(hex(p)[2:]) <= set("bcdf")

%o def aupton(limit): return [p for p in primerange(1, limit+1) if ok(p)]

%o print(aupton(769487)) # _Michael S. Branicky_, Nov 13 2021

%o (Python) # faster version for going to large numbers

%o from sympy import isprime

%o from itertools import product

%o def auptohd(m): # terms up to m hex digits

%o return [t for t in (int("".join(p), 16) for d in range(1, m+1) for p in product("bcdf", repeat=d)) if isprime(t)]

%o print(auptohd(7)) # _Michael S. Branicky_, Nov 13 2021

%Y Cf. A140969.

%K nonn,base

%O 1,1

%A _N. J. A. Sloane_, Feb 19 2014, corrected Feb 20 2014

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 8 20:37 EST 2021. Contains 349596 sequences. (Running on oeis4.)