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A276118 Numbers n such that 42 * 10^n + 1 is prime. 0
0, 1, 2, 4, 13, 19, 39, 62, 76, 79, 109, 184, 222, 265, 370, 626, 670, 679, 763, 1950, 2174, 3379, 7369, 9087, 34990, 47535, 97970 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,3
COMMENTS
For n > 0, numbers such that the digits 42 followed by n - 1 occurrences of the digit 0 followed by the digit 1 is prime (see the Example section).
a(28) > 10^5.
LINKS
Makoto Kamada, Search for 420w1.
EXAMPLE
4 is in this sequence because 42*10^4+1 = 420001 is prime.
Initial terms and primes associated:
a(1) = 0, 43;
a(2) = 1, 421;
a(3) = 2, 4201;
a(4) = 4, 420001;
a(5) = 13, 420000000000001, etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[42 * 10^# + 1] &]
PROG
(PARI) is(n)=ispseudoprime(42*10^n+1) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
Sequence in context: A176126 A240096 A018761 * A179114 A356288 A082015
KEYWORD
nonn,more
AUTHOR
Robert Price, Aug 20 2016
STATUS
approved

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Last modified March 29 02:23 EDT 2024. Contains 371264 sequences. (Running on oeis4.)