A068838 Smallest prime with concatenation of first n even numbers as leading digits.

2, 241, 2467, 24683, 2468101, 246810121, 24681012149, 24681012141601, 2468101214161811, 246810121416182039, 24681012141618202211, 2468101214161820222441, 246810121416182022242641, 246810121416182022242628043, 24681012141618202224262830073

Offset

1,1

Comments

a(350) has 1001 digits. - Michael S. Branicky, Mar 19 2024

Links

Michael S. Branicky, Table of n, a(n) for n = 1..349 (terms 1..300 from Harvey P. Dale with corrections to terms 1..175 by Sean A. Irvine and corrections in 176..300 by Michael S. Branicky)

Prog

(Python)
from sympy import isprime
from itertools import count
def a(n):
    if n == 1: return 2
    prefix = int("".join(map(str, (2*i for i in range(1, n+1)))))
    for extra in count(1):
        prefix *= 10
        for i in range(10**extra):
            t = prefix + i
            if isprime(t): return t
print([a(n) for n in range(1, 16)]) # Michael S. Branicky, Mar 19 2024

Crossrefs

Sequence in context: A006523 A294319 A055968 * A074256 A146312 A109930

Adjacent sequences: A068835 A068836 A068837 * A068839 A068840 A068841

Keyword

nonn,base

Author

Amarnath Murthy, Mar 09 2002

Extensions

More terms from Benoit Cloitre, Mar 10 2002

Corrected by T. D. Noe, Nov 15 2006

Corrected and extended by Jayanta Basu, Aug 09 2013

Data corrected by Sean A. Irvine, Mar 19 2024

Status

approved