A053922
Numbers k such that k^2 contains only digits {2,4,6}.
Original entry on oeis.org
2, 8, 68, 162, 668, 5162, 6668, 25738, 66668, 79162, 163238, 666668, 6666668, 8041408, 24993332, 66666668, 666666668, 6666666668, 8016649092, 66666666668, 666666666668, 6666666666668, 66666666666668
Offset: 1
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Select[Range[700000],SubsetQ[{2,4,6},IntegerDigits[#^2]]&] (* The program generates the first 12 terms of the sequence. To generate more, increase the Range constant but the program may take a long time to run. *) (* Harvey P. Dale, Jun 16 2022 *)
More terms from C. Ronaldo (aga_new_ac(AT)hotmail.com), Jan 04 2005
A119160
Triangular numbers composed of digits {2,4,6}.
Original entry on oeis.org
6, 66, 666, 426426, 266262426, 22464262666, 46624464466426, 644644226644644222426, 46424226426466426446424262644446, 626644642222466644646226466422666
Offset: 1
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[t: n in [1..2*10^7] | Set(Intseq(t)) subset {2, 4, 6} where t is n*(n+1) div 2]; // Vincenzo Librandi, Feb 04 2016
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F:= proc(d) # get all terms with d digits
local res, m, prefs,i,t,qmax,qmin,smax,smin,cand,s;
res:= NULL;
m:= max(1,floor(d/2-1));
prefs:= [2,4,6]*10^(d-1);
for i from 1 to m-1 do
prefs:= map(t -> (t + 2*10^(d-1-i),t+4*10^(d-1-i),t+6*10^(d-1-i)), prefs)
od;
for t in prefs do
qmax:= t + 6*(10^(d-m)-1)/9; smax:= floor(sqrt(8*qmax+1));
qmin:= t + 2*(10^(d-m)-1)/9; smin:= ceil(sqrt(8*qmin+1));
smin:= smin + 1 - (smin mod 2);
for s from smin to smax by 2 do
cand:= (s^2 -1)/8;
if cand mod 10 = 6 and convert(convert(cand,base,10),set) subset {2,4,6} then
res:= res, cand;
fi
od
od;
res;
end proc:
seq(F(d),d=1..21); # Robert Israel, Feb 05 2016
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Select[#*(# + 1)/2 & /@
Range[1000000], !
MemberQ[IntegerDigits[#], 0 | 1 | 3 | 5 | 7 | 8 | 9] &] (*Julien Kluge, Feb 01 2016*)
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