A337219 a(n) is the least positive number k such that 3^n+k has n prime factors counted with multiplicity.

2, 1, 1, 3, 9, 7, 21, 63, 157, 471, 5, 15, 45, 135, 405, 1215, 3645, 10935, 32805, 98415, 295245, 885735, 2657205, 4409119, 2741597, 8224791, 16285765, 15302863, 45908589, 137725767, 77632981, 232898943, 161825917, 485477751, 1456433253, 3027122479, 1565174669

Offset: 1

Author

Zak Seidov, Sep 14 2020

Keywords

• nonn

Links

• David A. Corneth, Table of n, a(n) for n = 1..56

Crossrefs

Cf. A078843.

Programs

Mathematica

a[n_] := Module[{k = 1}, While[PrimeOmega[3^n + k] != n, k++]; k]; Array[a, 20] (* Amiram Eldar, Sep 18 2020 *)

PARI

a(n) = for(k=1, oo, if(bigomega(3^n+k)==n,return(k))); \\ Daniel Suteu, Oct 17 2020

Extensions

a(27)-a(37) from Daniel Suteu, Sep 14 2020

Definition edited by Zak Seidov, Oct 17 2020