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A068105 Smallest prime starting with n 5s. 5
2, 5, 557, 5557, 555521, 555557, 55555517, 55555553, 5555555501, 5555555557, 555555555551, 555555555551, 5555555555551, 555555555555529, 555555555555557, 55555555555555519, 555555555555555559, 555555555555555559, 55555555555555555567, 5555555555555555555087 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,1
LINKS
FORMULA
a(n) <= A065588(n). - Michael S. Branicky, Feb 05 2021
PROG
(Python)
from sympy import isprime
def a(n):
if n < 2: return list([2, 5])[n]
n5s, i, pow10 = int('5'*n), 1, 1
while True:
i = 1
while i < pow10:
t = n5s * pow10 + i
if isprime(t): return t
i += 2
pow10 *= 10
print([a(n) for n in range(20)]) # Michael S. Branicky, Feb 05 2021
CROSSREFS
Sequence in context: A133378 A283561 A037063 * A065588 A208277 A131748
KEYWORD
base,easy,nonn
AUTHOR
Amarnath Murthy, Feb 20 2002
EXTENSIONS
Edited and extended by Robert G. Wilson v, Feb 21 2002
Corrected by Don Reble, Jan 17 2007
STATUS
approved

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Last modified March 29 03:51 EDT 2024. Contains 371264 sequences. (Running on oeis4.)