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A281020 Numbers with a prime number of raised dots in their Braille representation. 1

%I

%S 0,1,4,6,8,12,13,15,19,21,31,47,51,67,70,74,76,78,87,91,100,104,106,

%T 108,111,127,137,140,144,146,148,157,160,164,166,168,172,173,175,177,

%U 179,180,184,186,188,197,202,203,205,207,209,217,220,224,226,228,230,234,236,238

%N Numbers with a prime number of raised dots in their Braille representation.

%H Indranil Ghosh, <a href="/A281020/b281020.txt">Table of n, a(n) for n = 1..10000</a>

%H Indranil Ghosh, <a href="/A281020/a281020_1.txt">Braille Numerals</a>

%e 67 is in the sequence. 67, as evident from the link uploaded above, has 11 raised dots ("o") in its Braille representation and 11 is prime.

%o (Python)

%o from sympy import isprime

%o B=[3, 1, 2, 2, 3, 2, 3, 4, 3, 2]

%o def a(n):

%o s=0

%o for i in str(n):

%o s+=B[int(i)]

%o return s+4

%o i=0

%o j=1

%o while j<=10000:

%o if isprime(a(i))==True :

%o print str(j)+" "+str(i)

%o j+=1

%o i+=1

%Y Cf. A072283, A281015, A281017.

%K nonn,base

%O 1,3

%A _Indranil Ghosh_, Jan 13 2017

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Last modified October 21 02:29 EDT 2021. Contains 348141 sequences. (Running on oeis4.)