|
| |
|
|
A028985
|
|
Nonsquare palindromes whose sum of divisors is odd.
|
|
1
|
|
|
|
2, 8, 242, 20402, 24642, 2004002, 2138312, 2468642, 85099058, 200040002, 204060402, 242484242, 291080192, 20000400002, 20442824402, 24204840242, 29956665992, 88484148488, 297738837792, 2000004000002, 2004006004002, 2040608060402, 2420048400242
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
1,1
|
|
|
COMMENTS
|
Palindromes of the form 2*k^2, with k a nonzero integer. - Stéphane Rézel, Jan 04 2018
|
|
|
LINKS
|
Stéphane Rézel, Table of n, a(n) for n = 1..68
Proof Wiki, Sigma_Function_Odd_iff_Argument_is_Square_or_Twice_Square
|
|
|
MATHEMATICA
|
Select[Array[2 #^2 &, 10^7], PalindromeQ] (* Michael De Vlieger, Jan 10 2018 *)
|
|
|
PROG
|
(PARI) for(n=1, 10^9, my(d=digits(2*n^2)); if(d==Vecrev(d), print1(2*n^2, ", "))); \\ Joerg Arndt, Jan 10 2018
|
|
|
CROSSREFS
|
Sequence in context: A009588 A338543 A125264 * A067583 A120378 A012345
Adjacent sequences: A028982 A028983 A028984 * A028986 A028987 A028988
|
|
|
KEYWORD
|
nonn,base
|
|
|
AUTHOR
|
Patrick De Geest
|
|
|
EXTENSIONS
|
Offset corrected and a(14)-a(21) from Donovan Johnson, Apr 25 2010
a(22)-a(23) from Donovan Johnson, Jun 16 2011
|
|
|
STATUS
|
approved
|
| |
|
|
