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A121172 Smallest integer k>0 such that k*10^n + 1 is a prime. 4
1, 1, 3, 7, 7, 22, 3, 6, 6, 3, 19, 18, 4, 39, 6, 13, 37, 15, 15, 6, 16, 9, 96, 61, 19, 6, 9, 3, 33, 63, 57, 117, 55, 49, 30, 3, 28, 6, 42, 24, 36, 72, 21, 60, 6, 24, 33, 61, 21, 85, 31, 49, 13, 93, 18, 90, 9, 16, 135, 19, 55, 9, 135, 60, 6, 30, 3, 16, 115, 114, 19, 99, 15, 147, 171, 42 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..76.

FORMULA

a(n) = (A070854(n)-1)/10^n. - Chandler

EXAMPLE

a(1) = 1 because A030430[1] = 11 is a smallest prime of form 10*k + 1.

a(2) = 1 because A062800[1] = 101 is a smallest prime of form 100*k + 1.

CROSSREFS

Cf. A030430, A062800, see A070854 for resulting primes.

Sequence in context: A226512 A270307 A261480 * A322934 A077629 A184467

Adjacent sequences:  A121169 A121170 A121171 * A121173 A121174 A121175

KEYWORD

nonn

AUTHOR

Alexander Adamchuk, Aug 14 2006

EXTENSIONS

Minor edits by Ray Chandler, Feb 10 2009

STATUS

approved

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Last modified September 15 12:22 EDT 2019. Contains 327078 sequences. (Running on oeis4.)