A068837 Smallest prime with concatenation of first n odd numbers as leading digits.

11, 13, 13513, 13577, 135799, 135791107, 13579111307, 1357911131503, 13579111315171, 135791113151719, 1357911131517192157, 13579111315171921231, 135791113151719212325007, 1357911131517192123252763, 13579111315171921232527291, 135791113151719212325272931

Offset

1,1

Comments

a(351) has 1002 digits. - Michael S. Branicky, Mar 19 2024

Links

Michael S. Branicky, Table of n, a(n) for n = 1..350

Prog

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

Crossrefs

Sequence in context: A360388 A096074 A288611 * A246627 A257135 A357046

Adjacent sequences: A068834 A068835 A068836 * A068838 A068839 A068840

Keyword

nonn,base

Author

Amarnath Murthy, Mar 09 2002

Extensions

More terms from Benoit Cloitre, Mar 10 2002

a(10) corrected by Jayanta Basu, Aug 08 2013

a(6)-a(8) and a(13) corrected and more terms from Sean A. Irvine, Mar 17 2024

Status

approved