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A278328
Numbers n such that abs(n - rev(n)) is a square, where rev(n) is the decimal reverse of n (A004086).
2
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 15, 21, 22, 23, 26, 32, 33, 34, 37, 40, 43, 44, 45, 48, 51, 54, 55, 56, 59, 62, 65, 66, 67, 73, 76, 77, 78, 84, 87, 88, 89, 90, 95, 98, 99, 101, 111, 121, 131, 141, 151, 161, 171, 181, 191, 202, 212, 222, 232, 242, 252, 262
OFFSET
1,3
COMMENTS
All palindromes are in this sequence, hence it is infinite.
LINKS
MAPLE
a:= proc(n) option remember; local k; for k from 1+
`if`(n=1, -1, a(n-1)) while not issqr(abs(k-(s->
parse(cat(s[-i]$i=1..length(s))))(""||k))) do od: k
end:
seq(a(n), n=1..100); # Alois P. Heinz, Nov 18 2016
MATHEMATICA
Select[Range@ 262, IntegerQ@ Sqrt@ Abs[# - FromDigits@ Reverse@ IntegerDigits@ #] &] (* Michael De Vlieger, Nov 18 2016 *)
PROG
(Python 2.7.7)
import math
n = 0
while True:
if math.sqrt(abs(n-int(str(n)[::-1])))%1 == 0:
print n
n += 1 # Jonathan Frech, Nov 18 2016
(PARI) is(n) = issquare(abs(n - eval(concat(Vecrev(Str(n)))))) \\ Felix Fröhlich, Nov 18 2016
(PARI) is(n, {b=10}) = issquare(abs(n - subst(Polrev(digits(n, b), 'x), 'x, b))); \\ Gheorghe Coserea, Nov 27 2016
CROSSREFS
A002113 is a subsequence.
Sequence in context: A071204 A002796 A055471 * A066254 A167904 A347769
KEYWORD
nonn,base
AUTHOR
Jonathan Frech, Nov 18 2016
STATUS
approved