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A249915
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Numbers n such that the decimal expansions of both n and n^2 have 2 as smallest digit and 6 as largest digit.
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10
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255465, 652244, 665256, 2534665, 2536656, 2554262, 6523462, 6524235, 6652242, 23352656, 23354365, 23523462, 23546665, 23565325, 25346665, 25425256, 25624665, 25625465, 65226242, 65234535, 235442656, 254234662, 255465525, 255645525, 256246665, 256254665
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internal format)
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OFFSET
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1,1
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LINKS
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MAPLE
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M:= 10:
B:= [[2], [3], [4], [5], [6]]:
A:= NULL:
for d from 2 to M do
B:= map(b -> seq([op(b), i], i=2..6), B);
C:= select(b -> max(b)=6 and min(b) = 2, B);
X:= map(b -> add(b[i]*10^(d-i), i=1..d), C);
X:= select(proc(x) local L; L:= convert(x^2, base, 10); max(L) = 6 and min(L) = 2 end proc, X);
A:= A, op(X);
od:
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MATHEMATICA
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fQ[n_] := Block[{d = DigitCount@ n}, Plus @@ Prepend[Take[d, -4], First@ d] == 0 && d[[2]] > 0 && d[[6]] > 0]; Select[Range@ 2600000, fQ@ # && fQ[#^2] &] (* Michael De Vlieger, Apr 27 2015 *)
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PROG
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(PARI) is(n) = vecmin(digits(n))==2 && vecmin(digits(n^2))==2 && vecmax(digits(n))==6 && vecmax(digits(n^2))==6
(Python)
from itertools import product
for l in range(10):
....for a in product('23456', repeat = l):
........for b in ('2', '4', '5', '6'):
............s = ''.join(a)+b
............if '2' in s and '6' in s:
................n = int(s)
................if {'2', '6'} <= set(str(n**2)) <= {'2', '3', '4', '5', '6'}:
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CROSSREFS
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Cf. A137067, A137079, A137093, A256630, A256631, A256633, A256634, A256708, A256709, A256889, A257197, A257210, A257211, A256601, A257310.
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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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