This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A370482 #22 Jan 17 2025 09:29:34
%S A370482 1,0,2,1,1,1,1,1,1,0,1,1,1,1,1,0,1,1,1,1,1,0,1,1,1,0,1,0,1,1,1,1,1,0,
%T A370482 1,0,1,1,1,0,1,1,1,1,1,0,1,1,1,0,1,0,1,1,1,0,1,0,1,1,1,1,1,0,1,0,1,1,
%U A370482 1,0,1,1,1,1,1,0,1,0,1,1,1,0,1,1,1,0,1,0,1,1,1,0,1,0,1,0,1,1,1,0,1
%N A370482 Characteristic function of primes plus characteristic function of even numbers.
%C A370482 There is only one 2 in the sequence, so if the value 2 is blanked out, a riddle is created that demands some out-of-the-box thinking.
%H A370482 Antti Karttunen, <a href="/A370482/b370482.txt">Table of n, a(n) for n = 0..100000</a>
%F A370482 a(n) = A010051(n) + A059841(n).
%e A370482 1 is neither prime nor even so a(1) = 0 + 0 = 0.
%e A370482 2 is both a prime and even so a(2) = 1 + 1 = 2.
%e A370482 3 is a prime but odd so a(3) = 1 + 0 = 1.
%e A370482 4 is not a prime but even so a(4) = 0 + 1 = 1.
%t A370482 a[n_] := Boole[PrimeQ[n]] + Boole[EvenQ[n]]; Array[a, 100, 0] (* _Amiram Eldar_, Mar 31 2024 *)
%o A370482 (Python)
%o A370482 from sympy import isprime
%o A370482 def A370482(n): return isprime(n)+(n&1^1) # _Chai Wah Wu_, Apr 25 2024
%o A370482 (PARI) A370482(n) = (!(n%2) + isprime(n)); \\ _Antti Karttunen_, Jan 17 2025
%Y A370482 Cf. A010051, A059841.
%Y A370482 If a(2) were 1 instead of 2, then this would the characteristic function of {0} U A106092, whose complement A014076 gives the positions of 0's. - _Antti Karttunen_, Jan 17 2025
%K A370482 nonn,easy
%O A370482 0,3
%A A370482 _Jens Ahlström_, Mar 31 2024