A105179 Numbers having in decimal representation the same final digit as their largest proper divisor has; a(1) = 1.

1, 11, 15, 20, 25, 31, 40, 41, 45, 60, 61, 71, 75, 80, 100, 101, 105, 120, 121, 125, 131, 135, 140, 143, 151, 160, 165, 175, 180, 181, 187, 191, 195, 200, 209, 211, 220, 225, 240, 241, 251, 253, 255, 260, 271, 275, 280, 281, 285, 300, 311, 315, 319, 320, 325

Offset: 1

Author

Reinhard Zumkeller, Apr 29 2005

Keywords

• nonn
• base

Comments

A010879(A032742(a(n))) = A010879(a(n));

A008602 is a subsequence apart from the initial term;

A030430 is a subsequence.

Examples

			n=105=3*35 and 105 == 35 modulo 10, therefore 105 is a term.
		

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
• Index entries for sequences related to final digits of numbers

Programs

Haskell

a105179 n = a105179_list !! (n-1)
a105179_list = 1 : filter (\x -> a010879 (a032742 x) == a010879 x) [2..]
-- Reinhard Zumkeller, Jan 10 2013

Mathematica

Join[{1},Select[Range[2,400],Last[IntegerDigits[Divisors[#][[-2]]]] == Last[IntegerDigits[#]]&]]  (* Harvey P. Dale, Apr 21 2011 *)

PARI

lpf(n)=factor(n)[1,1]
is(n)=if(n%2, n%15==0||n%25==0||n==1||lpf(n)%5==1, n%20==0) \\ Charles R Greathouse IV, Jan 02 2013