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A376002
Positions of records in A032662.
1
1, 3, 5, 22, 84, 99, 511, 803, 9999, 18887, 1378751, 103974046
OFFSET
1,2
COMMENTS
Numbers k such that the first j for which the concatenation j || j+k is prime is greater than for any previous k.
In order for j || j+k to be prime where j+k has d digits, k and 10^d+1 must be coprime.
EXAMPLE
a(5) = 84 because A032662(84) = 929 which is greater than A032662(k) for all k < 84.
MAPLE
tcat:= (a, b) -> a*10^(1+ilog10(b))+b:
f:= proc(n) local k, k0, d;
for d from ilog10(n)+1 do
if igcd(10^d+1, n) = 1 then
k0:= max(1, 10^(d-1)-n);
if (k0+n)::even then k0:= k0+1 fi;
for k from k0 to 10^d-n-1 by 2 do
if isprime(tcat(k, k+n)) then return k fi
od fi od
end proc:
R:= NULL: m:= 0: count:= 0:
for i from 1 while count < 11 do
v:= f(i);
if v > m then
count:= count+1; m:= v; R:= R, i;
fi;
od:
R;
CROSSREFS
Sequence in context: A124423 A209109 A212260 * A178377 A270621 A270637
KEYWORD
nonn,base,more
AUTHOR
Robert Israel, Sep 05 2024
STATUS
approved