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Search: id:A161721
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| A161721 |
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Primes p such that the reversal of p is prime and the product of p with its reversal is a palindrome. |
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+0
1
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| 2, 3, 11, 101, 1021, 1201, 111211, 112111, 1000211, 1010201, 1020101, 1101211, 1102111, 1111021, 1112011, 1120001, 1121011, 1201111, 10011101, 10012001, 10021001, 10100201, 10111001, 10200101, 11012011, 11021011, 11100121
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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This sequence is a subsequence of A062936. If you multiply a member of this sequence by its reversal you get a number fixed under TITO algorithm (see A161594)
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LINKS
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T. Khovanova, Turning Numbers Inside Out [From Tanya Khovanova (tanyakh(AT)yahoo.com), Jul 07 2009]
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EXAMPLE
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1021 is a prime number, its reversal is 1201, which is also a prime. The product 1021*1201 = 1226221 is a palindrome.
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MAPLE
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rev := proc (n) local nn: nn := convert(n, base, 10): add(nn[j]*10^(nops(nn)-j), j = 1 .. nops(nn)) end proc: a := proc (n) local p: p := ithprime(n): if isprime(rev(p)) = true and rev(p*rev(p)) = p*rev(p) then p else end if end proc: seq(a(n), n = 1 .. 800000); [From Emeric Deutsch (deutsch(AT)duke.poly.edu), Jun 26 2009]
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MATHEMATICA
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Select[Range[10000000], PrimeQ[ # ] && PrimeQ[rev[ # ]] && prodRev[ # ] == rev[prodRev[ # ]] &]
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CROSSREFS
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Cf. A161594, A161597, A161600
Sequence in context: A056899 A117699 A065378 this_sequence A079853 A050721 A058114
Adjacent sequences: A161718 A161719 A161720 this_sequence A161722 A161723 A161724
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KEYWORD
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base,nonn
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AUTHOR
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Tanya Khovanova (tanyakh(AT)yahoo.com), Jun 17 2009
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EXTENSIONS
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Edited by N. J. A. Sloane, Jun 23 2009
More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Jun 26 2009
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