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A085733
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Right-truncatable semiprimes.
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3
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4, 6, 9, 46, 49, 62, 65, 69, 91, 93, 94, 95, 466, 469, 493, 497, 622, 623, 626, 629, 655, 694, 695, 697, 698, 699, 913, 914, 917, 933, 934, 939, 943, 949, 951, 955, 958, 959, 4661, 4666, 4667, 4694, 4699, 4934, 4939, 4971, 4979, 6227, 6233, 6238
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OFFSET
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1,1
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COMMENTS
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Semiprimes in which repeatedly deleting the rightmost digit gives a semiprime at every step until a single digit semiprime remains.
The sequence is finite. According to Shyam Sunder Gupta (guptass(AT)rediffmail.com) the number 95861957783594714393831931415189937897 is the largest right-truncatable semiprime.
The total number of right-truncatable semiprimes including the single digit semiprimes 4, 6 and 9 is 56076. So sequence is finite. - Shyam Sunder Gupta (guptass(AT)rediffmail.com), Jan 13 2008
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REFERENCES
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Angell, I. O. and Godwin, H. J. "On Truncatable Primes." Math. Comput. 31, 265-267, 1977.
Shyam Sunder Gupta, "Truncatable Semi-primes",Mathematical Spectrum, Vol. 39,No.3(2007), pp. 109-112.
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LINKS
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Table of n, a(n) for n=1..50.
Index entries for sequences related to truncatable primes
G. L. Honaker, Jr., Prime Curios!
Shyam Sunder Gupta, The largest right-truncatable semiprime. Prime Curios.
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CROSSREFS
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Cf. A001358, A213019.
Sequence in context: A215477 A175459 A107665 * A107342 A086698 A115666
Adjacent sequences: A085730 A085731 A085732 * A085734 A085735 A085736
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KEYWORD
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base,fini,nonn
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AUTHOR
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G. L. Honaker, Jr., Jul 20 2003
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EXTENSIONS
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More terms from Reinhard Zumkeller, Jul 22 2003
More terms from Hugo Pfoertner, Jul 22, 2003
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STATUS
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approved
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