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A167417 Largest prime concatenation of the first n primes, or 0 if no such prime exists. 3
2, 23, 523, 7523, 751123, 75311213, 7523171311, 753217131911, 75323219131117, 0, 753312923219111713, 75373312923192171311, 7541373132923217111319, 754341373132923192171311, 75474341373132923211171319 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
a(10) doesn't exist, because the sum of digits of the first 10 primes (2+3+5+7+(1+1)+(1+3)+(1+7)+(1+9)+(2+3)+(2+9)) = 57 is a multiple of 3.
REFERENCES
Richard E. Crandall and Carl Pomerance, Prime Numbers, Springer 2005.
Paulo Ribenboim, The New Book of Prime Number Records, Springer 1996.
A. Weil, Number theory: an approach through history, Birkhäuser 1984.
LINKS
EXAMPLE
The only prime concatenations of the first n primes for n = 1..3 are a(1)=2, a(2)=23, and a(3)=523.
For n=4, the only prime concatenations of 2, 3, 5, and 7 are 2357, 2753, 3257, 3527, 5237, 5273, 7253, 7523; the largest of these is a(4) = 7523.
PROG
(Python)
from sympy import sieve, isprime
from itertools import permutations
for n in range(1, 14):
sieve.extend_to_no(n)
p = list(map(str, list(sieve._list)))[:n]
mint = 0
for i in permutations(p, len(p)):
t = int(''.join(i))
if t > mint and isprime(t):
mint = t
print(mint, end = ', ') # Gleb Ivanov, Dec 05 2021
CROSSREFS
Sequence in context: A053160 A167416 A053066 * A053161 A090731 A090314
KEYWORD
nonn,base
AUTHOR
Eva-Maria Zschorn (e-m.zschorn(AT)zaschendorf.km3.de), Nov 03 2009
EXTENSIONS
Edited by Charles R Greathouse IV, Apr 28 2010
Several terms corrected and a(11)-a(15) from Gleb Ivanov, Dec 05 2021
STATUS
approved

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Last modified March 29 02:22 EDT 2024. Contains 371264 sequences. (Running on oeis4.)