|
%I #43 Aug 07 2022 12:59:43
%S 0,1,4,9,10,18,40,46,52,61,63,90,94,100,121,144,148,163,169,180,400,
%T 423,441,460,484,487,520,522,526,610,630,652,675,676,691,900,925,927,
%U 940,961,982,1000,1042,1062,1089,1210,1251,1273,1297,1405,1426,1440,1480
%N Numbers whose reversal is a square.
%C Every power of 10 is a term in the sequence.
%C If k is in the sequence then so is 10*k. - _David A. Corneth_, Aug 06 2022
%C If all multiples of 10 were omitted, A074896 would result. - _Jon E. Schoenfield_, Aug 06 2022
%e 0 is a term, 0 -> 0 (0^2).
%e 10 is a term, 10 -> 01 (leading zero is dropped) (1^2).
%e 691 is a term, 691 -> 196 (14^2).
%e 1800 is a term, 1800 -> 0081 (leading zeros are dropped) (9^2).
%t Select[Range[0, 1500], IntegerQ[Sqrt[IntegerReverse[#]]] &] (* _Amiram Eldar_, Aug 06 2022 *)
%o (Python)
%o from sympy import integer_nthroot
%o def ok(n):
%o return integer_nthroot(int(str(n)[::-1]), 2)[1]
%o print([k for k in range(1500) if ok(k)])
%o (Python)
%o from math import isqrt
%o from itertools import count, islice
%o def A356417_gen(): # generator of terms
%o yield 0
%o for l in count(1):
%o nlist = []
%o for m in range(1,isqrt(10**l)+1):
%o if m%10:
%o s = str(m**2)
%o nlist.append(int(s[::-1])*10**(l-len(s)))
%o yield from sorted(nlist)
%o A356417_list = list(islice(A356417_gen(),100)) # _Chai Wah Wu_, Aug 07 2022
%o (PARI) isok(k) = issquare(fromdigits(Vecrev(digits(k)))); \\ _Michel Marcus_, Aug 06 2022
%Y Cf. A002942, A004086, A074896.
%K nonn,base
%O 1,3
%A _Daniel Blam_, Aug 06 2022
|
