A175760 Numbers n such that d(n + d(n)) = d(n), where d(n) is the sum of the distinct primes dividing n.

1, 2, 39, 95, 119, 182, 2130, 2183, 2356, 2623, 3059, 3431, 3825, 6680, 9588, 10170, 10679, 11790, 14039, 14111, 15030, 16199, 16762, 16799, 17766, 19669, 22218, 24505, 26352, 26353, 34443, 34765, 34875, 36594, 37843, 39121, 39479, 39697, 42210, 44051, 45346

Offset: 1

Author

Michel Lagneau, Aug 28 2010

Keywords

• nonn

Comments

The sum of the distinct primes dividing n (A008472) sometimes called sopf(n).

d(1) = 0 because 1 has no prime divisors. So 1 is in this sequence because d(1+0) = d(1). - T. D. Noe, Jul 06 2012

Examples

			39 is in the sequence because sopf(39) = 16 and sopf(39 + sopf(39)) = sopf(55 ) = 16.
		

Links

• T. D. Noe, Table of n, a(n) for n = 1..1000

Programs

Mathematica

d[n_] := Plus @@ Transpose[FactorInteger[n]][[1]]; Join[{1}, Select[Range[2,50000], d[# + d[#]] == d[#] &]]