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 A223458 #24 Jun 25 2022 13:19:42 %S A223458 41,43,47,61,67,83,89,97,401,409,419,421,431,433,439,443,449,457,461, %T A223458 463,467,479,487,491,499,601,607,613,617,619,631,641,643,647,653,659, %U A223458 661,673,677,683,691,809,811,821,823,827,829,839,853,857,859,863,877,881 %N A223458 Primes whose first digit is a composite number. %H A223458 K. D. Bajpai, <a href="/A223458/b223458.txt">Table of n, a(n) for n = 1..10000</a> %e A223458 409 is a prime number whose first digit is 4, a composite number, so 409 is a term. %p A223458 KD := proc() local a,b,d,e; a:= ithprime(n); b:=length(a); d:=a/(10^(b-1)); e:=floor(d); if isprime(e)=false and e>1 then RETURN (a): fi; end: seq(KD(),n=1..200); %o A223458 (Python) %o A223458 from sympy import primerange %o A223458 from itertools import count, islice %o A223458 def agen(): yield from (p for e in count(1) for k in [4, 6, 8, 9] for p in primerange(k*10**e, (k+1)*10**e)) %o A223458 print(list(islice(agen(), 54))) # _Michael S. Branicky_, Jun 25 2022 %Y A223458 Cf. A069090 (primes none of whose proper initial segments are primes). %K A223458 nonn,base %O A223458 1,1 %A A223458 _K. D. Bajpai_, Aug 24 2013