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A084122
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Numbers k such that k*prime(k) is a palindrome.
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9
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1, 2, 5, 12, 16, 3623, 4119, 618725, 708567, 1498739, 2762990591
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listen;
history;
text;
internal format)
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OFFSET
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1,2
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COMMENTS
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LINKS
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EXAMPLE
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4119 is in the sequence since the 4119th prime is 39119 and 4199*39119 = 161131161 is a palindrome.
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MAPLE
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ispal:= proc(n) local L;
L:= convert(n, base, 10);
L = ListTools:-Reverse(L);
end proc:
R:= NULL: count:= 0: p:= 1:
for k from 1 while count < 11 do
p:= nextprime(p);
if ispal(k*p) then R:= R, k; count:= count+1 fi
od:
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MATHEMATICA
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palQ[n_]:=FromDigits[Reverse[IntegerDigits[n]]]==n; t={}; Do[If[palQ[Prime[n]*n], AppendTo[t, n]], {n, 15*10^5}]; t (* Jayanta Basu, May 11 2013 *)
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PROG
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(PARI) ispal(n) = my(d=digits(n)); d == Vecrev(d); \\ A002113
(Python)
from sympy import sieve
def ok(n): return n and (s := str(n*sieve[n])) == s[::-1]
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CROSSREFS
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KEYWORD
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base,nonn,more
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AUTHOR
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STATUS
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approved
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