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A086673 Number of right-truncatable semiprimes <= n. 5
0, 0, 0, 1, 1, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 6, 6, 6, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 10, 11, 12, 12, 12, 12 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,6

LINKS

Table of n, a(n) for n=1..98.

I. O. Angell and H. J. Godwin, On Truncatable Primes, Math. Comput. 31, 265-267, 1977.

Eric Weisstein's World of Mathematics, Semiprime

Index entries for sequences related to truncatable primes

CROSSREFS

Cf. A085733, A001358.

Sequence in context: A230516 A192688 A156752 * A101787 A269024 A244160

Adjacent sequences:  A086670 A086671 A086672 * A086674 A086675 A086676

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Jul 27 2003

STATUS

approved

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Last modified February 16 21:59 EST 2019. Contains 320200 sequences. (Running on oeis4.)