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A045708
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Primes with first digit 2.
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24
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2, 23, 29, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 2003, 2011, 2017, 2027, 2029, 2039, 2053, 2063, 2069, 2081, 2083, 2087, 2089, 2099, 2111, 2113, 2129, 2131, 2137, 2141, 2143, 2153, 2161, 2179, 2203, 2207, 2213, 2221
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OFFSET
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1,1
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LINKS
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FORMULA
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See A045707 for comments on density of these sequences.
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MATHEMATICA
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Select[Table[Prime[n], {n, 3000}], First[IntegerDigits[#]]==2 &] (* Vincenzo Librandi, Aug 08 2014 *)
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PROG
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(Haskell)
a045708 n = a045708_list !! (n-1)
a045708_list = filter ((== 2) . a000030) a000040_list
(Magma) [p: p in PrimesUpTo(2300) | Intseq(p)[#Intseq(p)] eq 2]; // Vincenzo Librandi, Aug 08 2014
(Python)
from sympy import isprime
def agen(limit=float('inf')):
yield 2
digits, adder = 1, 20
while True:
for i in range(1, 10**digits, 2):
test = adder + i
if test > limit: return
if isprime(test): yield test
digits, adder = digits+1, adder*10
agento = lambda lim: agen(limit=lim)
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CROSSREFS
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For primes with initial digit d (1 <= d <= 9) see A045707, A045708, A045709, A045710, A045711, A045712, A045713, A045714, A045715; A073517, A073516, A073515, A073514, A073513, A073512, A073511, A073510, A073509
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KEYWORD
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nonn,base,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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