A180925 Natural numbers with palindromic number of divisors.

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70

Offset

1,2

Comments

The first natural number not in this sequence is 48, which has 10 divisors. The complement of this sequence begins 48, 60, 72, 80, 84, 90, 96, 108, 112, 120, 126, 132, 140, 144, 150, 156, 160, 162, 168, 176, 180, 192, 198, 200, ... - Nathaniel Johnston, May 27 2011

Links

Nathaniel Johnston, Table of n, a(n) for n = 1..10000

Maple

read(transforms): with(numtheory): A180925 := proc(n) option remember: local k, t: if(n=1)then return 1: fi: for k from procname(n-1)+1 do t:=tau(k): if(t=digrev(t))then return k: fi: od: end: seq(A180925(n), n=1..100); # Nathaniel Johnston, May 27 2011

Crossrefs

Cf. A000005, A002113.

Sequence in context: A268200 A296873 A044923 * A272302 A272443 A272437

Adjacent sequences: A180922 A180923 A180924 * A180926 A180927 A180928

Keyword

base,easy,nonn

Author

Giovanni Teofilatto, Sep 25 2010

Status

approved