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

%I A281020 #12 Feb 21 2025 16:44:28
%S A281020 0,1,4,6,8,12,13,15,19,21,31,47,51,67,70,74,76,78,87,91,100,104,106,
%T A281020 108,111,127,137,140,144,146,148,157,160,164,166,168,172,173,175,177,
%U A281020 179,180,184,186,188,197,202,203,205,207,209,217,220,224,226,228,230,234,236,238
%N A281020 Numbers with a prime number of raised dots in their Braille representation.
%H A281020 Indranil Ghosh, <a href="/A281020/b281020.txt">Table of n, a(n) for n = 1..10000</a>
%H A281020 Indranil Ghosh, <a href="/A281020/a281020_1.txt">Braille Numerals</a>
%e A281020 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 A281020 (Python)
%o A281020 from sympy import isprime
%o A281020 B=[3, 1, 2, 2, 3, 2, 3, 4, 3, 2]
%o A281020 def a(n):
%o A281020     s=0
%o A281020     for i in str(n):
%o A281020         s+=B[int(i)]
%o A281020     return s+4
%o A281020 i=0
%o A281020 j=1
%o A281020 while j<=10000:
%o A281020     if isprime(a(i))==True :
%o A281020         print(f"{j} {i}")
%o A281020         j+=1
%o A281020     i+=1
%Y A281020 Cf. A072283, A281015, A281017.
%K A281020 nonn,base
%O A281020 1,3
%A A281020 _Indranil Ghosh_, Jan 13 2017