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 A281252 #31 Mar 25 2017 16:22:39 %S A281252 2,3,5,43,115,619,1249,1681,1711,2563,2635,5155,10321,10531,11539, %T A281252 13219,14479,17713,17755,18217,18889,20203,20905,26335,27163,29305, %U A281252 35353,39859,40867,40897,40993,44425,44803,51145,52993,55735,57751,58075,68335,68839,69553 %N A281252 Numbers whose septenary, octal and nonary representations are prime when read in decimal. %C A281252 After a(1) all the terms are odd. %C A281252 After a(2) all terms are relatively prime to 42. - _Charles R Greathouse IV_, Jan 22 2017 %H A281252 Charles R Greathouse IV, <a href="/A281252/b281252.txt">Table of n, a(n) for n = 1..10000</a> %e A281252 a(6) = 619 is in the sequence because 619_10 = 1543_7 = 1153_8 = 757_9; and 1543, 1153 and 757 are prime when read in decimal. %e A281252 a(7) = 1249 is in the sequence because 1249_10 = 3433_7 = 2341_8 = 1637_9; and 3433, 2341 and 1637 are prime when read in decimal. %t A281252 Select[Range[500000], PrimeQ[FromDigits[IntegerDigits[#, 7]]] && PrimeQ[FromDigits[IntegerDigits[#, 8]]] && PrimeQ[FromDigits[IntegerDigits[#, 9]]] &] %o A281252 (PARI) is(n)=for(b=7,9, if(!isprime(fromdigits(digits(n,b))), return(0))); 1 \\ _Charles R Greathouse IV_, Jan 22 2017 %Y A281252 Cf. A065726, A065727, A138299, A175279, A236365. %K A281252 nonn,base %O A281252 1,1 %A A281252 _K. D. Bajpai_, Jan 22 2017