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A085733 Right-truncatable semiprimes. 3


%S 4,6,9,46,49,62,65,69,91,93,94,95,466,469,493,497,622,623,626,629,655,

%T 694,695,697,698,699,913,914,917,933,934,939,943,949,951,955,958,959,

%U 4661,4666,4667,4694,4699,4934,4939,4971,4979,6227,6233,6238

%N Right-truncatable semiprimes.

%C Semiprimes in which repeatedly deleting the rightmost digit gives a semiprime at every step until a single-digit semiprime remains.

%C The sequence is finite. According to Shyam Sunder Gupta the number 95861957783594714393831931415189937897 is the largest right-truncatable semiprime.

%C The total number of right-truncatable semiprimes including the single digit semiprimes 4, 6 and 9 is 56076. - _Shyam Sunder Gupta_, Jan 13 2008

%D Shyam Sunder Gupta, Truncatable semi-primes, Mathematical Spectrum 39:3 (2007), pp. 109-112.

%H <a href="/index/Tri#tprime">Index entries for sequences related to truncatable primes</a>

%H I. O. Angell and H. J. Godwin, <a href="http://www.ams.org/journals/mcom/1977-31-137/S0025-5718-1977-0427213-2/S0025-5718-1977-0427213-2.pdf">On truncatable primes</a>, Math. Comput. 31:137, 265-267, 1977.

%H G. L. Honaker, Jr., <a href="http://primes.utm.edu/curios/page.php?short=46613113151331733179">Prime Curios!</a>

%H Shyam Sunder Gupta, <a href="http://primes.utm.edu/curios/page.php?curio_id=6861">The largest right-truncatable semiprime.</a> Prime Curios.

%Y Cf. A001358, A213019.

%K base,fini,nonn

%O 1,1

%A _G. L. Honaker, Jr._, Jul 20 2003

%E More terms from _Reinhard Zumkeller_, Jul 22 2003

%E More terms from _Hugo Pfoertner_, Jul 22 2003

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Last modified June 24 09:37 EDT 2019. Contains 324323 sequences. (Running on oeis4.)