login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A033294 Squares which when written backwards remain square (final 0's excluded). 5
1, 4, 9, 121, 144, 169, 441, 484, 676, 961, 1089, 9801, 10201, 10404, 10609, 12321, 12544, 12769, 14641, 14884, 40401, 40804, 44521, 44944, 48841, 69696, 90601, 94249, 96721, 698896, 1002001, 1004004, 1006009, 1022121, 1024144, 1026169 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Of this sequence's first 10000 terms, only nine have an even number of digits; see A354256.

LINKS

Jon E. Schoenfield, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Reinhard Zumkeller)

Index entry for sequences related to reversing digits of squares

EXAMPLE

144 = 12 * 12 is a term because 441 = 21 * 21.

MATHEMATICA

Select[Range[1100]^2, Mod[#, 10]!=0&&IntegerQ[Sqrt[FromDigits[Reverse[ IntegerDigits[ #]]]]]&] (* Harvey P. Dale, Oct 28 2013 *)

PROG

(Haskell)

a033294 n = a033294_list !! (n-1)

a033294_list = filter chi a000290_list where

  chi m = m `mod` 10 > 0 && head ds `elem` [1, 4, 5, 6, 9] &&

          a010052 (foldl (\v d -> 10 * v + d) 0 ds) == 1 where

    ds = unfoldr

         (\x -> if x == 0 then Nothing else Just $ swap $ divMod x 10) m

-- Reinhard Zumkeller, Jan 19 2012

(Python)

from math import isqrt

from itertools import count, islice

def sqr(n): return isqrt(n)**2 == n

def agen():

    yield from (k*k for k in count(1) if k%10 and sqr(int(str(k*k)[::-1])))

print(list(islice(agen(), 36))) # Michael S. Branicky, May 21 2022

CROSSREFS

Cf. A007488, A007500, A354256.

Sequence in context: A324024 A042381 A230743 * A156317 A115676 A115667

Adjacent sequences:  A033291 A033292 A033293 * A033295 A033296 A033297

KEYWORD

base,nonn

AUTHOR

Jeff Burch

EXTENSIONS

More terms from Erich Friedman

Initial 0 removed and offset changed by Reinhard Zumkeller, Jan 19 2012

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 8 10:26 EDT 2022. Contains 356009 sequences. (Running on oeis4.)