A137612 -id:A137612 - cp's OEIS frontend

A137611 Lesser of a pair of distinct closest n-digit primes that add up to 10^n.

3, 47, 491, 4919, 49877, 499943, 4999913, 49999757, 499999931, 4999999937, 49999999811, 499999999769, 4999999998431, 49999999999619, 499999999999769, 4999999999998557, 49999999999998887, 499999999999999679

Offset: 1

Lekraj Beedassy, Jan 29 2008

Hans Havermann, Table of n, a(n) for n = 1..50

Apart from initial term, same as A124450.

Cf. A137612, A124450.

Edited by N. J. A. Sloane May 15 2008 at the suggestion of R. J. Mathar.

A-number in cross-reference corrected by R. J. Mathar, Jul 17 2009

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

A137611 Lesser of a pair of distinct closest n-digit 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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