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

1,2

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.

Links

Table of n, a(n) for n=1..44.

Example

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

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 *)

Crossrefs

Cf. A338565, A328928.

Sequence in context: A318761 A020153 A307866 * A286373 A286372 A151760

Adjacent sequences: A338924 A338925 A338926 * A338928 A338929 A338930

Keyword

nonn

Author

Robert Israel, Nov 15 2020

Status

approved