A071861 Numbers k such that the largest prime factor of k is equal to the sum of primes dividing k+1 (with repetition).

5, 44, 51, 3103, 3145, 3509, 3737, 3887, 4929, 6024, 6344, 9085, 10286, 10787, 11725, 12035, 13052, 14314, 14816, 14839, 19071, 19662, 20513, 23779, 27950, 28248, 35860, 36239, 41005, 45135, 48447, 50826, 52124, 53416, 59186, 64355

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Example

3145 is a term because 3145 = 5*17*37 and sopfr(3146) = 2+11+11+13 = 37.

Mathematica

seq = {}; gpfPrev = 0; Do[sopfr = Plus @@ Times @@@ (f = FactorInteger[n]); If[sopfr == gpfPrev, AppendTo[seq, n - 1]]; gpfPrev = f[[-1, 1]], {n, 2, 65000}]; seq (* Amiram Eldar, Dec 08 2019 *)

Crossrefs

Cf. A001414, A006530.

Sequence in context: A030698 A080284 A193458 * A159298 A262118 A173376

Adjacent sequences: A071858 A071859 A071860 * A071862 A071863 A071864

Keyword

nonn

Author

Jason Earls, Jun 09 2002

Extensions

Offset corrected by Amiram Eldar, Dec 08 2019

Status

approved