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A038862 Numbers ending with '7' that are the difference of two positive cubes. 1
7, 37, 117, 127, 217, 387, 397, 547, 657, 817, 1027, 1197, 1267, 1387, 1647, 1657, 1727, 2107, 2437, 2457, 2717, 2977, 3087, 3367, 3997, 4167, 4447, 4697, 4977, 5167, 5677, 5707, 6327, 6347, 6487, 6517, 7057, 7317, 7657, 7957, 8587, 8937, 9197, 9317 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

MAPLE

filter:= proc(n) local t, y, r;

for t in sort(convert(numtheory:-divisors(n), list)) do

r:= 12*n*t-3*t^4;

if r < 0 then return false fi;

if not issqr(r) then next fi;

y:= (sqrt(r)-3*t^2)/(6*t);

if y::posint then return true fi

od;

false

end proc:

select(filter, [seq(i, i=7..10000, 10)]); # Robert Israel, Aug 08 2019

MATHEMATICA

With[{nn=60}, Select[Union[#[[2]]-#[[1]]&/@Subsets[Range[nn]^3, {2}]], Mod[#, 10] == 7&&#<nn^3-(nn-1)^3&]] (* Harvey P. Dale, Jan 12 2022 *)

CROSSREFS

Cf. A181123.

Sequence in context: A159491 A106064 A282001 * A136204 A139891 A082113

Adjacent sequences: A038859 A038860 A038861 * A038863 A038864 A038865

KEYWORD

nonn,base

AUTHOR

Jeff Burch

EXTENSIONS

Name corrected by Robert Israel, Aug 08 2019

STATUS

approved

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Last modified December 6 05:22 EST 2022. Contains 358594 sequences. (Running on oeis4.)