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A327133 The difference between 10^n and the lesser of the twin primes immediately before. 1
5, 29, 119, 71, 11, 41, 29, 413, 809, 299, 239, 41, 1511, 29, 2033, 359, 1193, 1073, 1499, 2261, 5003, 2429, 1793, 4331, 833, 5879, 359, 779, 2813, 1061, 2099, 1811, 3281, 5201, 533, 5483, 1679, 1421, 26801, 12089, 2843, 27773, 9641, 10841, 4763, 2129, 1019, 20531, 8519, 14339 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
All terms are congruent to 5 (mod 6).
Records: 5, 29, 119, 413, 809, 1511, 2033, 2261, 5003, 5879, 26801, ..., 37058441, ... - Robert G. Wilson v, Dec 10 2019
LINKS
FORMULA
a(n) = A011557(n) - A092250(n).
EXAMPLE
a(1) = 5 because the greatest twin prime pair less than 10 is {5, 7};
a(2) = 29 since the greatest 2-digit twin prime pair is {71, 73};
a(3) = 119 since the greatest 3-digit twin prime pair is {881, 883}; etc.
MAPLE
f:= proc(n) local w, p, q;
w:= 10^n; q:= w;
do
p:= q;
q:= prevprime(p);
if p-q = 2 then return w-q fi;
od
end proc:
map(f, [$1..100]); # Robert Israel, Nov 28 2019
MATHEMATICA
p[n_] := Block[{d = PowerMod[10, n, 6]}, 10^n - NestWhile[# -6 &, 10^n -d -1, !PrimeQ[#] || !PrimeQ[# +2] &]]; Array[p, 50] (* updated Nov 29 2019 *)
PROG
(PARI) prectwin(n)=n++; while(!isprime(2+n=precprime(n-1)), ); n
a(n)=10^n - prectwin(10^n) \\ Charles R Greathouse IV, Nov 28 2019
CROSSREFS
Sequence in context: A297632 A153077 A000352 * A267921 A241676 A291889
KEYWORD
nonn
AUTHOR
Robert G. Wilson v, Nov 28 2019
STATUS
approved

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Last modified May 26 16:43 EDT 2024. Contains 372840 sequences. (Running on oeis4.)