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A250297 Number n such that the n-th term of "concatenate next digit at right hand end (where the next digit after 9 is again 1)" is a semiprime. 0
3, 4, 7, 13, 25, 34, 37, 97 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

First unknown: 361.

LINKS

Table of n, a(n) for n=1..8.

EXAMPLE

a(4) = 13 so 1234567891234 = 2 * 617283945617 is a semiprime.

CROSSREFS

Cf. A057137.

Sequence in context: A280224 A282718 A092406 * A254310 A121174 A050071

Adjacent sequences:  A250294 A250295 A250296 * A250298 A250299 A250300

KEYWORD

nonn,base

AUTHOR

Eric Chen, Dec 26 2014

STATUS

approved

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Last modified January 21 23:58 EST 2022. Contains 350481 sequences. (Running on oeis4.)