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A213019 Largest n-digit right-truncatable semiprime. 2
9, 95, 959, 9599, 95999, 959999, 9599999, 95999987, 959999879, 9599998799, 95999987999, 959999879999, 9599998791827, 95999987918279, 959999879182793, 9599998791715333, 95999987917153339, 959999879171533399, 9599998791715333999, 95999987917153339993 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

For the definition of a right-truncatable semiprime, see A213017. The largest possible right-truncatable semiprime a(38) = A085733(56076) = 95861957783594714393831931415189937897, found by S.S. Gupta, is the last term of this sequence.

LINKS

Hugo Pfoertner, Table of n, a(n) for n = 1..38 (all terms)

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

EXAMPLE

a(1) = 9 = 3*3

a(2) = 95 = 5*19 and none of 96, 97, 98, 99 semiprime

a(3) = 959 = 7*137

a(4) = 9599 = 29*331

a(5) = 95999 = 17*5647

a(6) = 959999 = 643*1493

a(7) = 9599999 = 1019*9421

a(8) = 95999987 = 7349*13063, 9599998 = 2*4799999 and none of 95999988 ... 95999999 semiprime

CROSSREFS

Cf. A001358, A085733, A213017, A213018.

Sequence in context: A115071 A000562 A193216 * A098450 A065456 A052389

Adjacent sequences:  A213016 A213017 A213018 * A213020 A213021 A213022

KEYWORD

nonn,base,fini,full

AUTHOR

Hugo Pfoertner, Jun 27 2012

STATUS

approved

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Last modified June 19 06:47 EDT 2019. Contains 324218 sequences. (Running on oeis4.)