OFFSET
1,2
COMMENTS
A000005(a(n)) = 1, 2, 3, 4, 6, 8, 18, 28, 36, 42, 48, 72, 96, 108, 128, 144, 168, 192, 336, 384, .... - Felix Fröhlich, May 19 2021
From Jon E. Schoenfield, Jun 22 2021: (Start)
There exists at least one m-digit term for every m in 1..22 except 21 (see the b-file).
Conjecture: all terms after a(1)=1 are even. (End)
LINKS
Jon E. Schoenfield, Table of n, a(n) for n = 1..59 (all terms < 10^22)
David A. Corneth, PARI program
Jon E. Schoenfield, C# program
EXAMPLE
Terms include: 4 (3 divisors); 6 (4 divisors); 44 (6 divisors); 66 (8 divisors); 252 (18 divisors).
MATHEMATICA
pal=Union@Flatten[Table[r=IntegerDigits@n; FromDigits/@(Join[r, #]&/@{Reverse@r, Rest@Reverse@r}), {n, 10^5}]]; m=0; lst={}; Do[s=DivisorSigma[0, k]; If[s>m, AppendTo[lst, k]; m=s], {k, pal}]; lst (* Giorgos Kalogeropoulos, Dec 08 2021 *)
PROG
(C#) // See C# link. Jon E. Schoenfield, Jun 19 2021
(PARI) \\ See PARI link. David A. Corneth, May 18 2021
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Bhupendra Kumar Singh, May 17 2021
EXTENSIONS
Data corrected and extended by David A. Corneth, May 18 2021
STATUS
approved