A349486 a(1) = 2. a(n) is the smallest number in A349484, which is not an earlier term and for which a(n-1) + a(n) is in A349484.

2, 3, 4, 5, 225, 18, 9, 27, 21, 6, 48, 108, 72, 36, 156, 54, 81, 111, 400, 7, 20, 210, 306, 135, 153, 288, 112, 224, 100, 8, 10, 902, 1168, 192, 324, 180, 50, 230, 900, 201, 280, 420, 209, 511, 407, 481, 702, 216, 405, 243, 378, 486, 432, 480, 621, 351, 513, 648

Offset

1,1

Links

Table of n, a(n) for n=1..58.

Example

a(1) = 2 and a(2) = 3 are Niven numbers with derivatives 2' = 1 and 3' = 1 which are Niven numbers, and a(1) + a(2) = 2 + 3 = 5 which is Niven number and 5' = 1 is also a Niven number.

Prog

(Magma) f:=func<n |n le 1 select 0 else n*(&+[Factorisation(n)[i][2] / Factorisation(n)[i][1]: i in [1..#Factorisation(n)]])>; a:=[]; niven:=func<n|n mod &+Intseq(n) eq 0 >; ff:=func<n|niven(n) and niven(Floor(f(n)))>; a:=[2]; for n in [2..58] do k:=3; while k in a or not(ff(k) and ff(k+a[n-1])) do k:=k+1; end while; Append(~a, k); end for; a;

Crossrefs

Cf. A003415 (arithmetic derivative), A005349 (Niven numbers), A349484.

Sequence in context: A037436 A377073 A115900 * A010347 A004878 A032546

Adjacent sequences: A349483 A349484 A349485 * A349487 A349488 A349489

Keyword

nonn,base

Author

Marius A. Burtea, Nov 20 2021

Status

approved