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A249915 Numbers n such that the decimal expansions of both n and n^2 have 2 as smallest digit and 6 as largest digit. 10
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Chai Wah Wu, Table of n, a(n) for n = 1..2000 (n = 1..42 from Robert Israel).

MAPLE

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:

A; # Robert Israel, Apr 27 2015

MATHEMATICA

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 *)

PROG

(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

A249915_list = []

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'}:

....................A249915_list.append(n) # Chai Wah Wu, Apr 29 2015

CROSSREFS

Cf. A137067, A137079, A137093, A256630, A256631, A256633, A256634, A256708, A256709, A256889, A257197, A257210, A257211, A256601, A257310.

Sequence in context: A168352 A147579 A087025 * A161534 A052197 A053076

Adjacent sequences:  A249912 A249913 A249914 * A249916 A249917 A249918

KEYWORD

nonn,base

AUTHOR

Felix Fröhlich, Apr 21 2015

STATUS

approved

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Last modified May 17 22:15 EDT 2021. Contains 343992 sequences. (Running on oeis4.)