login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A220627 Prime numbers that are not Brazilian. 15

%I #34 May 01 2021 07:36:41

%S 2,3,5,11,17,19,23,29,37,41,47,53,59,61,67,71,79,83,89,97,101,103,107,

%T 109,113,131,137,139,149,151,163,167,173,179,181,191,193,197,199,223,

%U 227,229,233,239,251,257,263,269,271,277,281,283,293,311,313,317

%N Prime numbers that are not Brazilian.

%C These are primes not in A085104 (Brazilian primes).

%C Primes that are not repunit in any base b >= 2 with three or more digits.

%H T. D. Noe, <a href="/A220627/b220627.txt">Table of n, a(n) for n = 1..1000</a>

%H Bernard Schott, <a href="/A125134/a125134.pdf">Les nombres brésiliens</a>, Quadrature, no. 76, avril-juin 2010, pages 30-38; included here with permission from the editors of Quadrature.

%t brazBases[n_] := Select[Range[2, n - 2], Length[Union[IntegerDigits[n, #]]] == 1 &]; Select[Range[2, 1000], PrimeQ[#] && brazBases[#] == {} &] (* _T. D. Noe_, Dec 26 2012 *)

%o (Python)

%o from sympy.ntheory.factor_ import digits

%o from sympy import isprime, primerange

%o def B(n):

%o l=[]

%o for b in range(2, n - 1):

%o d=digits(n, b)[1:]

%o if max(d)==min(d): l.append(n)

%o return l

%o print([n for n in primerange(2, 1001) if not B(n)]) # _Indranil Ghosh_, Jun 22 2017

%o (PARI) isok(p) = {if (isprime(p), for (b=2, p-1, my(d=digits(p, b), md=vecmin(d)); if ((#d > 2) && (md == 1) && (vecmax(d) == 1), return (0));); return (1););} \\ _Michel Marcus_, Apr 30 2021

%Y Cf. A085104.

%K nonn,base

%O 1,1

%A _Bernard Schott_, Dec 17 2012

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 29 06:34 EDT 2024. Contains 371265 sequences. (Running on oeis4.)