A335572 - OEIS

%I #19 Jan 28 2021 11:13:36

%S 2,3,4,4,5,6,5,7,8,6,9,6,10,7,11,12,7,8,13,14,9,15,8,16,8,10,17,18,9,

%T 11,19,20,9,12,21,10,22,13,23,24,10,11,14,25,10,26,15,27,12,28,11,16,

%U 29,30,11,13,17,31,32,12,18,33,14,34,19,35,12,36,12,13,15,20,37

%N Irregular triangle whose row n is the set of numbers d+n/d where d is a divisor of n.

%C The last term of row n is n+1.

%H Michel Marcus, <a href="/A335572/b335572.txt">Rows n=1..4000 of triangle, flattened</a>

%e Triangle begins:

%e   [2]

%e   [3]

%e   [4]

%e   [4, 5]

%e   [6]

%e   [5, 7]

%e   [8]

%e   [6, 9]

%e   [6, 10]

%e   [7, 11]

%e   ...

%t Table[Map[# + n/# &, #[[-Ceiling[Length[#]/2] ;; -1 ]] ] &@ Divisors[n], {n, 36}] // Flatten (* _Michael De Vlieger_, Jan 27 2021 *)

%o (PARI) row(n) = my(d=divisors(n)); Set(vector(#d,k,d[k]+n/d[k]));

%Y Cf. A027750 (divisors of n), A038548 (row lengths), A063655 (1st column).

%K nonn,tabf

%O 1,1

%A _Michel Marcus_, Jan 26 2021