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A223458
Primes whose first digit is a composite number.
2
41, 43, 47, 61, 67, 83, 89, 97, 401, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 601, 607, 613, 617, 619, 631, 641, 643, 647, 653, 659, 661, 673, 677, 683, 691, 809, 811, 821, 823, 827, 829, 839, 853, 857, 859, 863, 877, 881
OFFSET
1,1
LINKS
EXAMPLE
409 is a prime number whose first digit is 4, a composite number, so 409 is a term.
MAPLE
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);
PROG
(Python)
from sympy import primerange
from itertools import count, islice
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))
print(list(islice(agen(), 54))) # Michael S. Branicky, Jun 25 2022
CROSSREFS
Cf. A069090 (primes none of whose proper initial segments are primes).
Sequence in context: A005846 A273756 A154498 * A243429 A345346 A062669
KEYWORD
nonn,base
AUTHOR
K. D. Bajpai, Aug 24 2013
STATUS
approved