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A053547 Smallest prime starting with A000422(n). 2
11, 211, 3217, 432121, 543217, 65432117, 76543217, 876543211, 9876543211, 1098765432101, 11109876543211, 12111098765432101, 1312111098765432139, 141312111098765432113, 15141312111098765432173 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
EXAMPLE
a(6)=65432117 is smallest prime beginning with the string 654321.
MATHEMATICA
Flatten[Select[Join[10 #+Range[1, 9, 2], 100 #+Range[1, 99, 2]], PrimeQ, 1]&/@ Table[FromDigits[Flatten[IntegerDigits/@Range[n, 1, -1]]], {n, 25}]] (* Harvey P. Dale, Nov 04 2011 *)
PROG
(Python)
from sympy import isprime
def A053547(n):
s = int(''.join(str(m) for m in range(n, 0, -1)))
for i in range(1, 10):
s *= 10
for j in range(1, 10**i, 2):
x = s+j
if isprime(x):
return x
else:
return 'search limit reached.' # Chai Wah Wu, Jan 02 2015
CROSSREFS
Cf. A000422.
Sequence in context: A136307 A249604 A038399 * A053582 A077714 A089567
KEYWORD
easy,nice,nonn,base
AUTHOR
Enoch Haga, Jan 16 2000
STATUS
approved

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Last modified June 23 11:27 EDT 2024. Contains 373644 sequences. (Running on oeis4.)