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 A262210 #27 Sep 17 2015 08:45:23 %S A262210 12,13,15,17,43,45,47,67,83,93,95,97,103,107,113,123,125,127,129,131, %T A262210 137,141,143,147,153,157,159,161,163,165,167,171,173,179,183,185,187, %U A262210 193,197,402,403,405,407,411,413,417,419,423,429,431,437,441,443,447,453,459,461,467,471 %N A262210 Numbers whose decimal digits are the concatenation of a nonprime followed by a prime. %o A262210 (PARI) is(n)=if(gcd(n,10)>1,return(!isprime(n\10) && n>9 && isprime(n%10))); for(k=1,#Str(n)-1, if(isprime(n%10^k) && !isprime(n\10^k), return(1))); 0 \\ _Charles R Greathouse IV_, Sep 15 2015 %Y A262210 Cf. A125664. %K A262210 nonn,base %O A262210 1,1 %A A262210 _Giovanni Teofilatto_, Sep 15 2015