The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A280969 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A280969

Numbers k such that 7*10^k - 17 is prime.
(history; published version)

#20 by Michael De Vlieger at Sun Jun 09 22:16:20 EDT 2024

STATUS

proposed

approved

#19 by Jon E. Schoenfield at Sun Jun 09 19:19:13 EDT 2024

STATUS

editing

proposed

#18 by Jon E. Schoenfield at Sun Jun 09 19:18:59 EDT 2024

COMMENTS

For k > 1, numbers k such that the digit 6 followed by k-2 occurrences of the digit 9 followed by the digits 83 is prime (see Example section).

LINKS

Makoto Kamada, <a href="https://stdkmd.net/nrr/prime/primedifficultyprime_difficulty.txt">Search for 69w83</a>.

EXAMPLE

3 is in this sequence because 7*10^3 - 17 = 6983 is prime.

Initial terms and primes associated primes:

STATUS

approved

editing

#17 by Michel Marcus at Wed May 31 14:27:13 EDT 2023

STATUS

reviewed

approved

#16 by Hugo Pfoertner at Wed May 31 14:19:29 EDT 2023

STATUS

proposed

reviewed

#15 by Robert Price at Wed May 31 14:12:11 EDT 2023

STATUS

editing

proposed

#14 by Robert Price at Wed May 31 14:12:00 EDT 2023

DATA

1, 2, 3, 11, 16, 33, 35, 37, 39, 42, 64, 94, 123, 136, 308, 309, 310, 357, 965, 1109, 2178, 8916, 9471, 18330, 62127, 252209

COMMENTS

a(2627) > 23*10^5.

EXTENSIONS

a(26) from Robert Price, May 31 2023

STATUS

approved

editing

#13 by Andrey Zabolotskiy at Mon Nov 22 09:57:26 EST 2021

STATUS

editing

approved

#12 by Andrey Zabolotskiy at Mon Nov 22 09:57:17 EST 2021

MAPLE

Select[Range[1, 100000], PrimeQ[7*10^# - 17] &]

MATHEMATICA

Select[Range[1, 100000], PrimeQ[7*10^# - 17] &]

#11 by Andrey Zabolotskiy at Mon Nov 22 09:57:02 EST 2021

EXAMPLE

a(5) = 16, 69999999999999983; etc. #t Select[Range[1, 100000], PrimeQ[7*10^# - 17] &]

a(5) = 16, 69999999999999983; etc.

MAPLE

Select[Range[1, 100000], PrimeQ[7*10^# - 17] &]

STATUS

approved

editing