LINKS
Michael S. Branicky, <a href="/A372207/b372207_1.txt">Table of n, a(n) for n = 1..500</a>
The OEIS is supported by the many generous donors to the OEIS Foundation.
Revision History for A372207
(Bold, blue-underlined text is an addition; faded, red-underlined text is aShowing entries 1-10 | older changes
a(n) is the smallest prime number that is obtained by concatenating 2 consecutive n-digit integers.
(history; published version)
(history; published version)
STATUS
proposed
approved
STATUS
editing
proposed
PROG
(Python)
from sympy import isprime
def a(n):
if n == 1: return 23
lb, ub = 10**(n-1), 10**n
for k in range(lb, ub, 2):
base = k*ub
for inc in [k-1, k+1]:
if inc >= lb and isprime(t:=base+inc):
return t
print([a(n) for n in range(1, 16)]) # Michael S. Branicky, May 19 2024
STATUS
proposed
editing
STATUS
editing
proposed
EXTENSIONS
More terms a(12) and beyond from Michael S. Branicky, May 19 2024
LINKS
Michael S. Branicky, <a href="/A372207/b372207_1.txt">Table of n, a(n) for n = 1..500</a>
STATUS
proposed
editing
STATUS
editing
proposed
DATA
23, 1213, 102101, 10021001, 1000810007, 100010100011, 10000241000023, 1000004210000041, 100000002100000003, 10000000081000000009, 1000000000810000000007, 100000000002100000000001, 10000000000021000000000001, 1000000000001010000000000011, 100000000000002100000000000003
EXTENSIONS
More terms from Michael S. Branicky, May 19 2024
STATUS
proposed
editing
STATUS
editing
proposed