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A047695 y such that y^2 = C(x,0) + C(x,1) + C(x,2) + C(x,3) is soluble. 1
0, 1, 2, 8, 24, 260, 8672 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

REFERENCES

R. K. Guy, Unsolved Problems in Number Theory, Section D3.

LINKS

Table of n, a(n) for n=0..6.

MATHEMATICA

r[x_] := Reduce[y >= 0 && 6*y^2 == (x + 1)*(x^2 - x + 6), {y}, Integers]; Reap[ Do[ If[r[x] =!= False, Sow[y /. ToRules[r[x]]]], {x, -10, 1000}]][[2, 1]] (* Jean-François Alcover, Jul 12 2012 *)

CROSSREFS

Cf. A047694.

Sequence in context: A214849 A141598 A071599 * A093842 A050971 A118855

Adjacent sequences:  A047692 A047693 A047694 * A047696 A047697 A047698

KEYWORD

nonn,fini,full,nice

AUTHOR

N. J. A. Sloane

STATUS

approved

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Last modified November 22 08:46 EST 2019. Contains 329389 sequences. (Running on oeis4.)