A076888 a(n) is the number of divisors of the n-th positive palindromic number.

1, 2, 2, 3, 2, 4, 2, 4, 3, 2, 4, 4, 6, 4, 8, 4, 8, 6, 2, 4, 3, 2, 4, 2, 4, 6, 2, 2, 4, 6, 8, 8, 6, 18, 4, 10, 8, 6, 4, 2, 4, 6, 4, 2, 6, 2, 2, 4, 6, 12, 8, 8, 12, 4, 10, 8, 9, 8, 4, 4, 12, 4, 4, 8, 4, 6, 12, 8, 8, 16, 4, 12, 8, 10, 12, 9, 8, 16, 4, 4, 2, 4, 6, 2, 4, 8, 2, 2, 8, 4, 18, 4, 10, 16, 12, 4

Offset

1,2

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Formula

a(n) = A000005(A002113(n+1)).

Example

a(11) = 4 because there are 4 divisors of 11th positive palindromic number (i.e., 22).

Mathematica

palQ[n_]:=Module[{idn=IntegerDigits[n]}, idn==Reverse[idn]]; DivisorSigma[ 0, #]&/@ Select[Range[1000], palQ] (* Harvey P. Dale, Nov 29 2014 *)

Crossrefs

Cf. A000005, A002113.

Sequence in context: A339915 A306509 A083867 * A357171 A355698 A087990

Adjacent sequences: A076885 A076886 A076887 * A076889 A076890 A076891

Keyword

base,nonn

Author

Shyam Sunder Gupta, Nov 25 2002

Status

approved