OFFSET
0,13
COMMENTS
Every positive integer is a factor of a palindrome, unless it is a multiple of 10 (D. G. Radcliffe, see Links).
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 0..2500
P. De Geest, Smallest multipliers to make a number palindromic.
EXAMPLE
a(12) = 5 since 5*12 = 60 (i.e. 060) is a palindrome.
MATHEMATICA
rz[n_]:=Module[{idn=IntegerDigits[n]}, While[Last[idn]==0, idn=Most[idn]]; idn]; k[n_]:=Module[{k=1, p}, p=k*n; While[rz[p]!=Reverse[rz[p]], k++; p=k*n]; k]; Join[ {1}, Array[k, 90]] (* Harvey P. Dale, Mar 06 2013 *)
PROG
(ARIBAS): stop := 50000000; for n := 0 to 100 do k := 1; test := true; while test and k < stop do m := omit_trailzeros(n*k); if test := m <> int_reverse(m) then inc(k); end; end; if k < stop then write(k, " "); else write(-1, " "); end; end;
(Haskell)
a061674 n = until ((== 1) . a136522 . a004151 . (* n)) (+ 1) 1
-- Reinhard Zumkeller, Jul 20 2012
CROSSREFS
KEYWORD
nonn,base,easy,nice
AUTHOR
Amarnath Murthy, Jun 17 2001
STATUS
approved