

A124664


Both k and its reverse are one more than a square.


2



1, 2, 5, 10, 50, 101, 626, 730, 1090, 2210, 5477, 7745, 10001, 10610, 71290, 227530, 1000001, 1010026, 1014050, 1040401, 2217122, 2676497, 5053505, 5631130, 6200101, 6265010, 7946762, 100000001, 101808101, 248157010, 10000000001, 10180608202, 10182828101
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,2


COMMENTS

The first digit for each term is either 1, 2, 5, 6 or 7.  Chai Wah Wu, May 25 2017


LINKS

Chai Wah Wu, Table of n, a(n) for n = 1..100
Erich Friedman, What's Special About This Number?. See 5477 and 7745.


EXAMPLE

5477 is in the sequence because 5477 = 74^2 + 1 and 7745 = 88^2 + 1.


MAPLE

r:= n> (s> parse(cat(s[i]$i=1..length(s))))(""n):
select(x> issqr(r(x)1), [n^2+1$n=0..150000])[]; # Alois P. Heinz, May 24 2017


MATHEMATICA

Select[Range[10000000], IntegerQ[Sqrt[ #  1]] && IntegerQ[Sqrt[FromDigits[Reverse[IntegerDigits[ # ]]]  1]] &]


CROSSREFS

A066618 is a subsequence of this sequence of numbers that do not end in 0. The sequence A027720 = Palindromes of form n^2 + 1  is a palindromic subsequence of this sequence.
Cf. A287389: both k and its reverse are one less than a square.
Sequence in context: A139010 A018472 A082593 * A076776 A020755 A018503
Adjacent sequences: A124661 A124662 A124663 * A124665 A124666 A124667


KEYWORD

nonn,base


AUTHOR

Tanya Khovanova, Dec 23 2006


EXTENSIONS

More terms from Alois P. Heinz, May 24 2017


STATUS

approved



