A370354 Composite numbers k that share a factor with sopfr(k), the sum of the primes dividing k, with repetition.

4, 8, 9, 16, 18, 24, 25, 27, 30, 32, 36, 42, 49, 50, 60, 64, 66, 70, 72, 78, 81, 84, 98, 100, 102, 105, 110, 114, 120, 121, 125, 126, 128, 130, 132, 138, 140, 144, 150, 154, 156, 160, 162, 168, 169, 170, 174, 180, 182, 186, 190, 192, 195, 196, 200, 204, 216, 220, 222, 228, 230, 231, 234, 238, 240

Offset

1,1

Comments

All prime powers, see A246547, are terms.

Links

Scott R. Shannon, Table of n, a(n) for n = 1..10000

Example

18 is a term as 18 = 2 * 3 * 3, and soprf(18) = 2 + 3 + 3 = 8, which shares a factor with 18.

Mathematica

fn[{a_, b_}]:=a*b; Select[Range[240], CompositeQ[#]&&ContainsAny[First/@FactorInteger[#], First/@FactorInteger[ Total[fn/@FactorInteger[#]]]]&] (* James C. McMahon, May 06 2024 *)

Crossrefs

Cf. A001414, A002808, A027746, A246547, A046346, A372524.

Sequence in context: A034023 A086368 A034024 * A299117 A339462 A140269

Adjacent sequences: A370351 A370352 A370353 * A370355 A370356 A370357

Keyword

nonn

Author

Scott R. Shannon, May 06 2024

Status

approved