A124049 -id:A124049 - cp's OEIS frontend

A108163 A124049(n)/3.

0, 1, 3, 27, 41, 19, 29, 81, 23, 21, 63, 77, 523, 127, 77, 481, 371, 107, 113, 451, 121, 173, 441, 501, 247, 407, 319, 351, 113, 1977, 707, 767, 677, 1591, 1579, 3427, 439, 43, 1291, 481, 129, 3923, 2757, 1779, 961, 2379, 2731, 2831

Offset: 1

Hans Havermann, Apr 26 2007

nonn

lnc[n_]:=Module[{c=0,t=10^n/2},While[!AllTrue[t+{c,-c},PrimeQ],c++];c]; Array[lnc,50]/3 (* Harvey P. Dale, Sep 28 2024 *)

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

Original entry on oeis.org

7, 53, 509, 5081, 50123, 500057, 5000087, 50000243, 500000069, 5000000063, 50000000189, 500000000231, 5000000001569, 50000000000381, 500000000000231, 5000000000001443, 50000000000001113, 500000000000000321, 5000000000000000339, 50000000000000001353, 500000000000000000363

Offset: 1

Lekraj Beedassy, Jan 29 2008

Robert Israel, Table of n, a(n) for n = 1..300

Cf. A124049, A137611.

f:= proc(n) local t,p;
  p:= 5*10^(n-1);
  do
    p:= nextprime(p);
    if isprime(10^n - p) then return p fi
  od
end proc:
map(f, [$1..30]); # Robert Israel, Jan 13 2025

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

a(n) = 5*10^(n-1) + A124049(n) for n > 1. - Robert Israel, Jan 12 2025

a(7)-a(30) from Charles R Greathouse IV, Sep 29 2008

More terms from Michel Marcus, Jan 13 2025

A135057 Largest semiprime whose prime factors add up to 10^n.

Original entry on oeis.org

25, 2491, 249919, 24993439, 2499984871, 249999996751, 24999999992431, 2499999999940951, 249999999999995239, 24999999999999996031, 2499999999999999964279, 249999999999999999946639, 24999999999999999997538239, 2499999999999999999999854839, 249999999999999999999999946639

Offset: 1

Lekraj Beedassy, Feb 11 2008

nonn

Lekraj Beedassy, Table of n, a(n) for n = 1..35

s={};f[{p_,e_}]:=e*p;Do[a=(10^n/2)^2;While[PrimeOmega[a]!=2||Total[f/@FactorInteger[a]]!=10^n,a=a-1];AppendTo[s,a],{n,11}];s (* James C. McMahon, Apr 13 2025 *)

a(n) = A124450(n)*(10^n - A124550(n)) {= A137611(n)*A137612(n) for n>1}.

a(n) = 100^n/4-(A124049(n))^2. - Zak Seidov, Feb 15 2008

cp's OEIS Frontend

A108163 A124049(n)/3.

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

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A135057 Largest semiprime whose prime factors add up to 10^n.

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