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 A267821 #16 Jun 29 2019 01:41:58 %S A267821 23,73,509,643,751,1093,1153,1481,1783,2029,6067,8011,8933,9613,16061, %T A267821 24763,30803,44203,64633,74521,82723,88003,94033,103171,106619,118669, %U A267821 126541,133321,154571,158293,163561,165883,179821,197339,202393,207643,225523,234733,264083,268003,284593,288661,324931 %N A267821 Primes whose base-9 representation is a square in base 10. %C A267821 Primes in the sequence A267769. %H A267821 Chai Wah Wu, <a href="/A267821/b267821.txt">Table of n, a(n) for n = 1..10000</a> %e A267821 73 in base 9 is 81, and 81 = 9^2 in base 10. %t A267821 Select[Prime@ Range@ 28000, IntegerQ@ Sqrt@ FromDigits@ IntegerDigits[#, 9] &] (* _Michael De Vlieger_, Jan 24 2016 *) %o A267821 (Python) %o A267821 from sympy import isprime %o A267821 A267821_list = [int(d,9) for d in (str(i**2) for i in range(1,10**6)) if max(d) < '9' and isprime(int(d,9))] # _Chai Wah Wu_, Feb 22 2016 %Y A267821 In other bases: A267817 - A267821, A241246, A267490. %K A267821 nonn,base %O A267821 1,1 %A A267821 _Christopher Cormier_, Jan 20 2016