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A174176 Numbers n such that 10^n-2*n+1 is prime. 5
2, 5, 14, 42, 72, 74, 354, 1176, 1274, 4815, 6885, 28214 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(13) > 10^5. - Robert Price, Mar 26 2015

LINKS

Table of n, a(n) for n=1..12.

MATHEMATICA

Select[Range[5000], PrimeQ[(10^# - 2 # + 1)] &] (* Vincenzo Librandi, Oct 05 2012 *)

PROG

(MAGMA) /* The code gives only the terms up to 354: */ [n: n in [1..600] | IsPrime(10^n-2*n+1) ]

(PARI) is(n)=ispseudoprime(10^n-2*n+1) \\ Charles R Greathouse IV, Feb 20 2017

CROSSREFS

Cf. A173837, A110065, A110066, A110067.

Sequence in context: A000660 A148325 A281594 * A298367 A025274 A132833

Adjacent sequences:  A174173 A174174 A174175 * A174177 A174178 A174179

KEYWORD

nonn,more

AUTHOR

Vincenzo Librandi, Mar 11 2010

EXTENSIONS

a(8)-a(10) from Vincenzo Librandi, Oct 05 2012

a(11)-a(12) from Robert Price, Mar 26 2015

STATUS

approved

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Last modified October 23 19:26 EDT 2021. Contains 348215 sequences. (Running on oeis4.)