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A085733 Right-truncatable semiprimes. 3
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

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 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. - Shyam Sunder Gupta, Jan 13 2008

REFERENCES

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

LINKS

Table of n, a(n) for n=1..50.

Index entries for sequences related to truncatable primes

I. O. Angell and H. J. Godwin, On truncatable primes, Math. Comput. 31:137, 265-267, 1977.

G. L. Honaker, Jr., Prime Curios!

Shyam Sunder Gupta, The largest right-truncatable semiprime. Prime Curios.

CROSSREFS

Cf. A001358, A213019.

Sequence in context: A175459 A257652 A107665 * A242751 A107342 A086698

Adjacent sequences:  A085730 A085731 A085732 * A085734 A085735 A085736

KEYWORD

base,fini,nonn

AUTHOR

G. L. Honaker, Jr., Jul 20 2003

EXTENSIONS

More terms from Reinhard Zumkeller, Jul 22 2003

More terms from Hugo Pfoertner, Jul 22, 2003

STATUS

approved

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Last modified April 30 16:28 EDT 2017. Contains 285670 sequences.