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A356417
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Numbers whose reversal is a square.
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0
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0, 1, 4, 9, 10, 18, 40, 46, 52, 61, 63, 90, 94, 100, 121, 144, 148, 163, 169, 180, 400, 423, 441, 460, 484, 487, 520, 522, 526, 610, 630, 652, 675, 676, 691, 900, 925, 927, 940, 961, 982, 1000, 1042, 1062, 1089, 1210, 1251, 1273, 1297, 1405, 1426, 1440, 1480
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OFFSET
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1,3
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COMMENTS
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Every power of 10 is a term in the sequence.
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LINKS
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EXAMPLE
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0 is a term, 0 -> 0 (0^2).
10 is a term, 10 -> 01 (leading zero is dropped) (1^2).
691 is a term, 691 -> 196 (14^2).
1800 is a term, 1800 -> 0081 (leading zeros are dropped) (9^2).
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MATHEMATICA
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Select[Range[0, 1500], IntegerQ[Sqrt[IntegerReverse[#]]] &] (* Amiram Eldar, Aug 06 2022 *)
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PROG
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(Python)
from sympy import integer_nthroot
def ok(n):
return integer_nthroot(int(str(n)[::-1]), 2)[1]
print([k for k in range(1500) if ok(k)])
(Python)
from math import isqrt
from itertools import count, islice
def A356417_gen(): # generator of terms
yield 0
for l in count(1):
nlist = []
for m in range(1, isqrt(10**l)+1):
if m%10:
s = str(m**2)
nlist.append(int(s[::-1])*10**(l-len(s)))
yield from sorted(nlist)
(PARI) isok(k) = issquare(fromdigits(Vecrev(digits(k)))); \\ Michel Marcus, Aug 06 2022
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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