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A295392 Numbers k such that 5*10^k + 57 is prime. 0
1, 2, 5, 8, 14, 23, 24, 26, 41, 62, 85, 137, 209, 446, 1424, 1783, 3301, 5503, 5928, 9593, 18671, 40189, 60655, 113586, 172692 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
For k > 1, numbers such that the digit 5 followed by k-2 occurrences of the digit 0 followed by the digits 57 is prime (see Example section).
a(26) > 2*10^5.
LINKS
Makoto Kamada, Search for 50w57
EXAMPLE
2 is in this sequence because 5*10^2 + 57 = 557 is prime.
Initial terms and primes associated:
a(1) = 1, 107;
a(2) = 2, 557;
a(3) = 5, 500057;
a(4) = 8, 500000057;
a(5) = 14, 500000000000057; etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[5*10^# + 57] &]
PROG
(PARI) isok(k) = isprime(5*10^k + 57); \\ Michel Marcus, Nov 22 2017
CROSSREFS
Sequence in context: A330378 A058578 A261526 * A023674 A281864 A304025
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Nov 21 2017
EXTENSIONS
a(24)-a(25) from Robert Price, Dec 28 2018
STATUS
approved

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Last modified March 29 06:44 EDT 2024. Contains 371265 sequences. (Running on oeis4.)