OFFSET
1,2
COMMENTS
EXAMPLE
a(10) = 467 with 467 = 0^4 + 15*(2*15+1) + (-1)*(3*(-1)+1).
a(25) = 3507 with 3507 = 6^4 + 33*(2*33+1) + 0*(3*0+1).
a(36) = 152177 with 152177 = 9^4 + (-266)*(2*(-266)+1) + 38*(3*38+1).
a(37) = 1277405 with 1277405 = 22^4 + (-655)*(2*(-655)+1) + (-249)*(3*(-249)+1).
MATHEMATICA
QQ[n_]:=QQ[n]=IntegerQ[Sqrt[12n+1]];
m=0; Do[r=0; Do[If[QQ[n-x^4-y(2y+1)], r=r+1; If[r>1, Goto[aa]]], {x, 0, n^(1/4)}, {y, -Floor[(Sqrt[8(n-x^4)+1]+1)/4], (Sqrt[8(n-x^4)+1]-1)/4}]; If[r==1, m=m+1; Print[m, " ", n]]; Label[aa], {n, 0, 152177}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Zhi-Wei Sun, Apr 16 2020
STATUS
approved