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A282116 Numbers k such that k-1/2*R(k) and k+1/2*R(k) are both positive squares, where R(k) is the digits reverse of k. 0
468, 4842, 27225, 235890, 21030930, 840827745 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Similar to rare numbers A035519.

No more terms < 10^12. - Lars Blomberg, Jul 12 2017

a(7), if it exists, is larger than 2*10^15. - Giovanni Resta, Jul 14 2017

LINKS

Table of n, a(n) for n=1..6.

EXAMPLE

(468 - 1/2*864)^(1/2) = (36)^(1/2) = 6  and (468 +1/2*864)^(1/2) = (900)^(1/2) = 30.

MAPLE

R:=proc(w) local x, y, z; x:=w; y:=0; for z from 1 to ilog10(x)+1 do y:=10*y+(x mod 10); x:=trunc(x/10); od; y; end:

P:=proc(q, k) local n; for n from 1 to q do

if n>k*R(n) then if frac(sqrt(n-k*R(n)))=0 and frac(sqrt(n+k*R(n)))=0

then print(n); fi; fi; od; end: P(10^9, 1/2);

CROSSREFS

Cf. A004086, A035519.

Sequence in context: A054756 A205415 A205408 * A281061 A270259 A205407

Adjacent sequences:  A282113 A282114 A282115 * A282117 A282118 A282119

KEYWORD

nonn,base,more

AUTHOR

Paolo P. Lava, Feb 16 2017

EXTENSIONS

a(6) from Lars Blomberg, Jul 12 2017

STATUS

approved

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Last modified October 23 15:50 EDT 2021. Contains 348214 sequences. (Running on oeis4.)