cp's OEIS Frontend

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.

A360508 Numbers k such that A300570(k) considered simply as a decimal string is prime.

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%I A360508 #21 Jul 11 2023 09:12:44
%S A360508 2,4,13,57,64,349
%N A360508 Numbers k such that A300570(k) considered simply as a decimal string is prime.
%H A360508 <a href="/index/Mo#MWP">Index entries for sequences related to Most Wanted Primes video</a>
%e A360508 A300570(4) = 10011101 = A000040(665267) is prime, so 4 is a term.
%e A360508 A300570(5) = 10110011101 = 6389*1582409 is composite, so 5 is not a term.
%t A360508 Select[Range[350], PrimeQ[FromDigits[Flatten[IntegerDigits[Range[#, 1, -1], 2]]]] &] (* _Amiram Eldar_, Feb 19 2023 *)
%o A360508 (Python)
%o A360508 from sympy import isprime
%o A360508 from itertools import count, islice
%o A360508 def agen(): # generator of terms
%o A360508     s = ""
%o A360508     for k in count(1):
%o A360508         s = bin(k)[2:] + s
%o A360508         if isprime(int(s)): yield k
%o A360508 print(list(islice(agen(), 5))) # _Michael S. Branicky_, Feb 19 2023
%Y A360508 Cf. A300570, A098780 (A300570 converted to base 10), A348792 (primes in A098780).
%K A360508 nonn,base,more
%O A360508 1,1
%A A360508 _N. J. A. Sloane_, Feb 19 2023
%E A360508 a(6) from _Alois P. Heinz_, Feb 19 2023