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A088639
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Smallest prime beginning with at least n n's (in decimal notation).
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3
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2, 11, 223, 3331, 44449, 555557, 66666629, 777777701, 888888883, 99999999907, 1010101010101010101039, 11111111111111111111111, 12121212121212121212121223, 1313131313131313131313131301, 141414141414141414141414141497, 15151515151515151515151515151501
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listen;
history;
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OFFSET
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0,1
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LINKS
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MAPLE
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a:= proc(n) local d, h, s;
s:= parse(cat(0, n$n));
for d from 0 do
for h to 10^d-1 do
if isprime(s+h) then return s+h fi
od:
s:= s*10;
od
end:
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PROG
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(PARI) A088639(n)={ local(p=10^#Str(n), d=1); n*=(p^n-1)/(p-1); until( (d*=10)*(n+1)>p=nextprime(n*d), ); p} /* M. F. Hasler, Jan 13 2009 */
(Python)
from sympy import isprime
def a(n):
if n == 0: return 2
nns, i, pow10 = int(str(n)*n), 1, 1
while True:
i = 1
while i < pow10:
t = nns * pow10 + i
if isprime(t): return t
i += 2
pow10 *= 10
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CROSSREFS
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KEYWORD
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base,easy,nonn
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AUTHOR
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EXTENSIONS
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More cross-references and initial term added by M. F. Hasler, Jan 13 2009
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STATUS
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approved
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