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

Author

Giovanni Teofilatto, Sep 25 2010

Keywords

• base
• easy
• nonn

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

Crossrefs

Cf. A000005, A002113.

Programs

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