A338927 Locations of records in A338565.

1, 4, 6, 8, 12, 24, 36, 48, 72, 96, 144, 192, 240, 288, 384, 432, 576, 864, 1152, 1440, 1728, 2304, 2880, 3456, 4320, 4608, 5184, 5760, 6912, 8640, 10368, 11520, 13824, 17280, 20736, 23040, 25920, 27648, 34560, 41472, 51840, 62208, 69120, 82944

Offset: 1

Author

Robert Israel, Nov 15 2020

Keywords

• nonn

Comments

The first term divisible by 3 is a(3)=6.

The first term divisible by 5 is a(13)=240.

The first term divisible by 11 is a(48)=190080.

Examples

			a(3) = 6 is in the sequence because A338565(6) = 3 is greater than A338565(n) for n < 6.
		

Crossrefs

Cf. A338565, A328928.

Programs

Maple

ispali:= proc(n) local L;
  L:= convert(n,base,10);
  evalb(L = ListTools:-Reverse(L))
end proc:
N:= 200000: # for terms <= N
Palis:= select(ispali, {$2..N}):
A338565:= Vector(N):
A338565[1]:= 1:
R:= 1: bestv:= 1:
A[1]:= 1:
for n from 2 to N do
  A[n]:=  add(A[n/d], d= numtheory:-divisors(n) intersect Palis);
    if A[n] > bestv then bestv:= A[n]; R:= R, n
od:
R;

Mathematica

Block[{a, s}, a[n_] := If[n == 1, n, Sum[If[(d < n && PalindromeQ[n/d]), a[d], 0], {d, Divisors[n]}]]; s = Array[a, 10^4]; Map[FirstPosition[s, #][[1]] &, Union@ FoldList[Max, s]] ] (* Michael De Vlieger, Nov 15 2020 *)