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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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS All palindromes are in this sequence, hence it is infinite. LINKS Alois P. Heinz, Table of n, a(n) for n = 1..20000 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 FrÃ¶hlich, 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. Cf. A000290, A004086, A016766, A056965. Sequence in context: A071204 A002796 A055471 * A066254 A167904 A004841 Adjacent sequences:  A278325 A278326 A278327 * A278329 A278330 A278331 KEYWORD nonn,base AUTHOR Jonathan Frech, Nov 18 2016 STATUS approved

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Last modified April 17 14:32 EDT 2021. Contains 343063 sequences. (Running on oeis4.)