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A186142 a(n) is the smallest suffix such that the numbers with k digits "9" prepended are primes for k = 1, 2, ...,n. 1
7, 7, 29, 907, 32207, 573217, 3136717, 4128253 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

See A186143 for the digit "3" case. The corresponding sequences with the digits "1" or "7" are not possible because if Xn and XXn are prime, then XXXn will be a multiple of 3 when X is 1 or 7.

LINKS

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

EXAMPLE

a(3) = 29 because 329, 3329, 33329 are primes.

MATHEMATICA

m=1; Table[While[d=IntegerDigits[m]; k=0; While[k++; PrependTo[d, 9]; k <= n && PrimeQ[FromDigits[d]]]; k <= n, m++]; m, {n, 6}]

CROSSREFS

Cf. A186069, A186070.

Sequence in context: A198341 A299338 A246039 * A188274 A255281 A255283

Adjacent sequences:  A186139 A186140 A186141 * A186143 A186144 A186145

KEYWORD

nonn,base

AUTHOR

Michel Lagneau, Feb 13 2011

STATUS

approved

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Last modified November 22 05:55 EST 2019. Contains 329388 sequences. (Running on oeis4.)