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A137612 Greater of a pair of closest (n-digit) distinct primes that add up to 10^n.

%I A137612 #15 Jan 13 2025 11:32:44
%S A137612 7,53,509,5081,50123,500057,5000087,50000243,500000069,5000000063,
%T A137612 50000000189,500000000231,5000000001569,50000000000381,
%U A137612 500000000000231,5000000000001443,50000000000001113,500000000000000321,5000000000000000339,50000000000000001353,500000000000000000363
%N A137612 Greater of a pair of closest (n-digit) distinct primes that add up to 10^n.
%H A137612 Robert Israel, <a href="/A137612/b137612.txt">Table of n, a(n) for n = 1..300</a>
%F A137612 a(n) = 5*10^(n-1) + A124049(n) for n > 1. - _Robert Israel_, Jan 12 2025
%p A137612 f:= proc(n) local t,p;
%p A137612   p:= 5*10^(n-1);
%p A137612   do
%p A137612     p:= nextprime(p);
%p A137612     if isprime(10^n - p) then return p fi
%p A137612   od
%p A137612 end proc:
%p A137612 map(f, [$1..30]); # _Robert Israel_, Jan 13 2025
%o A137612 (PARI) a(n) = local(t);n=10^n;t=nextprime(n/2+1);while(!isprime(n-t),t=nextprime(t+1));t \\ _Charles R Greathouse IV_, Sep 29 2008
%Y A137612 Cf. A124049, A137611.
%K A137612 nonn,base
%O A137612 1,1
%A A137612 _Lekraj Beedassy_, Jan 29 2008
%E A137612 a(7)-a(30) from _Charles R Greathouse IV_, Sep 29 2008
%E A137612 More terms from _Michel Marcus_, Jan 13 2025