Revision History for A104842
(Underlined text is an addition;
strikethrough text is a deletion.)
Showing entries 1-10
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#21 by Jon E. Schoenfield at Sat Dec 08 03:28:05 EST 2018
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#20 by Jon E. Schoenfield at Sat Dec 08 03:27:57 EST 2018
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#19 by Jon E. Schoenfield at Sat Dec 08 03:27:54 EST 2018
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| COMMENTS
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Note that values with indices n= = 22, 43, 55,... , ... are positions of primes with leading zeros, which is in particular manifest from a(42)=99, a(43)=98. See A198344 for the position of the "true" n-digit primes listed in A104841. - M. F. Hasler, Oct 23 2011
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| EXAMPLE
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a(1)=1 since the first single -digit prime found, 3, is at first place, hence a(1)=1,
a(2)=1 since the first two -digit prime found, 31, is at first place, hence a(2)=1,
a(3)=8 since the first three -digit prime found, 653, is at 8th place, hence a(3)=8, ...
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approved
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#18 by Alois P. Heinz at Sat Oct 01 16:48:15 EDT 2016
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#17 by Alois P. Heinz at Sat Oct 01 16:48:11 EDT 2016
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| NAME
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Position of the first sequence of n subsequent digits of piPi which form a prime.
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approved
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#16 by Jon E. Schoenfield at Fri Mar 27 23:01:25 EDT 2015
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#15 by Jon E. Schoenfield at Fri Mar 27 23:01:23 EDT 2015
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| COMMENTS
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Note that values with indices n=22, 43, 55,... are positions of primes with leading zeros, which is in particular manifest from a(42)=99, a(43)=98. See A198344 for the position of the "true" n-digit primes listed in A104841. - . - _M. F. Hasler, _, Oct 23 2011
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| EXAMPLE
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a(3)=8 since the first three digit prime found, 653, is at 8th place, hence a(3)=8,..., ...
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| MATHEMATICA
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pi = RealDigits[Pi, 10, 100][[1]]; f[n_] := Block[{k = 1}, While[ !PrimeQ[ FromDigits[ Take[pi, {k, k + n - 1}]]], k++ ]; k]; Table[ f[n], {n, 67}] (from }] (* _Robert G. Wilson v _, Mar 29 2005) *)
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| PROG
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(PARI) a(n)={for(c=-1, default(realprecision)-n-2, ispseudoprime(Pi\.1^(n+c)%10^n)&return(c+2)); error("Insufficient realprecision, please increase.")} \\ - .")} \\ _M. F. Hasler, _, Oct 23 2011
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#14 by Russ Cox at Fri Mar 30 17:31:12 EDT 2012
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| EXTENSIONS
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More terms from a(33) onward from _Robert G. Wilson v (rgwv(AT)rgwv.com), _, Mar 29 2005
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Discussion
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| Fri Mar 30
| 17:31
| OEIS Server: https://oeis.org/edit/global/156
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#13 by Russ Cox at Fri Mar 30 17:26:12 EDT 2012
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| AUTHOR
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_Zak Seidov (zakseidov(AT)yahoo.com), _, Mar 27 2005
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Discussion
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| Fri Mar 30
| 17:26
| OEIS Server: https://oeis.org/edit/global/139
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#12 by M. F. Hasler at Tue Oct 25 11:13:05 EDT 2011
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