A330821 a(1) = 1, a(2) = 2. Thereafter a(n+1) is the smallest number k such that A001414(k) = a(n) + a(n-1).

1, 2, 3, 5, 15, 51, 305, 1059, 4083, 117737, 3775459, 19465955, 952896293, 13613071346, 14565967639, 112716155924, 11073544747197, 637616871476643, 11027737075804991, 3056322734187753262, 542921033413649799807, 8189660342217563295915, 515222301162241572644117

Offset: 1

Author

David James Sycamore, Jan 02 2020

Keywords

• nonn

Examples

			sopfr(3) = 3 = 2 + 1, sopfr(15) = 8 = 3 + 5, etc.
		

Links

• Jinyuan Wang, Table of n, a(n) for n = 1..200

Crossrefs

Cf. A000045, A001414, A056240.

Programs

Mathematica

s[1] = 0; s[n_] := Plus @@ Times @@@ FactorInteger@n; a[1] = 1; a[2] = 2; a[n_] := a[n] = Module[{k = 1, sum = a[n - 1] + a[n - 2]}, While[s[k] != sum, k++]; k]; Array[a, 10] (* Amiram Eldar, Jan 02 2020 *)

Formula

a(n+1) = A056240(a(n) + a(n-1)).

Extensions

Data corrected by and more terms from Amiram Eldar and David A. Corneth, Jan 02 2020

Data corrected by Jinyuan Wang, Mar 08 2020