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A338715
Smallest prime ending with decimal expansion of n, for n relatively prime to 10.
4
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
OFFSET
1,1
COMMENTS
a(n) exists by Dirichlet's theorem.
MAPLE
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:
convert(V, list); # Robert Israel, Nov 11 2020
PROG
(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
print([a(n) for n in range(1, 64)]) # Michael S. Branicky, Nov 03 2021
CROSSREFS
Cf. A045572, A105888 (base 2 equivalent), A258190.
See A245193, A337834, A338716 for other versions.
Sequence in context: A344542 A334132 A245193 * A258190 A244471 A083968
KEYWORD
nonn,base,look
AUTHOR
N. J. A. Sloane, Nov 11 2020.
EXTENSIONS
More terms from Robert Israel, Nov 11 2020
STATUS
approved