A169802 Numbers k equal to A074036(k) = sum of primes from least to largest prime factor.

2, 3, 5, 7, 10, 11, 13, 17, 19, 23, 29, 31, 37, 39, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 155, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271

Offset

1,1

Comments

Union of primes (A000040) and A055233.

Links

Table of n, a(n) for n=1..61.

Erich Friedman, What's Special About This Number?

Mathematica

upto=500; a={}; Do[f=Map[First, FactorInteger[k]]; If[k==Total[Select[Range[First[f], Last[f]], PrimeQ]], AppendTo[a, k]], {k, upto}]; a (* Paolo Xausa, Nov 27 2021 *)

Prog

(PARI) select( {is_A169802(n, f=factor(n)[, 1])=n>1&&n==vecsum(primes([f[1], f[#f]]))}, [1..222]) \\ M. F. Hasler, Nov 24 2021

Crossrefs

Cf. A055233 (this without primes), A074036 (sum of primes from spf(n) to gpf(n)).

Cf. A020639 (spf: smallest prime factor), A006530 (gpf: greatest prime factor).

Sequence in context: A324813 A235050 A117286 * A194948 A266679 A285257

Adjacent sequences: A169799 A169800 A169801 * A169803 A169804 A169805

Keyword

nonn

Author

N. J. A. Sloane, May 24 2010

Status

approved