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A338715
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Smallest prime ending with decimal expansion of n, for n relatively prime to 10.
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4
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11, 3, 7, 19, 11, 13, 17, 19, 421, 23, 127, 29, 31, 233, 37, 139, 41, 43, 47, 149, 151, 53, 157, 59, 61, 163, 67, 269, 71, 73, 277, 79, 181, 83, 487, 89, 191, 193, 97, 199, 101, 103, 107, 109, 2111, 113, 1117, 3119, 3121, 1123, 127, 1129, 131, 4133, 137, 139, 2141, 2143, 5147, 149, 151, 1153, 157
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OFFSET
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1,1
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COMMENTS
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a(n) exists by Dirichlet's theorem.
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LINKS
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MAPLE
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N:= 100: # for a(1) to a(N)
V:= Vector(N):
count:= 0:
for n from 1 while count < N do
if igcd(n, 10)=1 then
count:= count+1;
d:= ilog10(n)+1;
for x from n by 10^d do
if isprime(x) then V[count]:= x; break fi
od
fi
od:
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PROG
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(Python)
from sympy import isprime
def a(n):
ending = 2*n - 1 + (n+1)//4 * 2 # A045572
i, pow10 = ending, 10**len(str(ending))
while not isprime(i): i += pow10
return i
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CROSSREFS
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KEYWORD
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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