A127018 Least s with s, t both semiprime and s+2n = t.

4, 6, 4, 6, 4, 9, 21, 6, 4, 6, 4, 9, 9, 6, 4, 6, 4, 10, 39, 6, 4, 14, 9, 9, 15, 6, 4, 6, 4, 9, 15, 10, 21, 6, 4, 10, 21, 6, 4, 6, 4, 9, 9, 6, 4, 14, 21, 10, 21, 6, 4, 14, 9, 10, 9, 6, 4, 6, 4, 9, 21, 9, 15, 6, 4, 9, 9, 6, 4, 6, 4, 14, 9, 10, 9, 6, 4, 10, 25, 6, 4, 14, 21, 9, 15, 6, 4, 9, 9, 14, 21, 10

Offset

1,1

Links

Table of n, a(n) for n=1..92.

Mathematica

sp=Select[Range[1000], PrimeOmega[#]==2&]; seq={}; Do[s=0; Until[PrimeOmega[sp[[s]]+2n]==2, s++]; AppendTo[seq, sp[[s]]], {n, 92}]; seq (* James C. McMahon, Dec 30 2024 *)

Prog

(PARI) a(n) = for (k=1, oo, if ((bigomega(k)==2) && bigomega(2*n+k)==2, return(k))); \\ Michel Marcus, Dec 30 2024

Crossrefs

Cf. A001358, A127019, A020483.

Sequence in context: A010711 A168428 A351126 * A083396 A142973 A181110

Adjacent sequences: A127015 A127016 A127017 * A127019 A127020 A127021

Keyword

nonn

Author

Rick L. Shepherd, Jan 02 2007

Status

approved