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A033682
Numbers of the form (q^2+(q+1)^2)*(r^2+(r+1)^2), q,r >= 1.
1
25, 65, 125, 169, 205, 305, 325, 425, 533, 565, 625, 725, 793, 905, 1025, 1105, 1325, 1469, 1525, 1565, 1681, 1825, 1885, 2105, 2125, 2353, 2405, 2501, 2725, 2825, 2873, 3065, 3425, 3445, 3485, 3625
OFFSET
1,1
COMMENTS
All terms == 1,3,5 or 9 (mod 10). - Robert Israel, Mar 20 2018
REFERENCES
G. Tenenbaum, pp. 268ff of R. L. Graham et al., eds., Mathematics of Paul Erdős I.
LINKS
MAPLE
N:= 10000: # to get all terms <= N
g:= n -> n^2+(n+1)^2:
sort(convert({seq(seq(g(q)*g(r), r = 1 .. floor((sqrt(2*N/g(q)-1)-1)/2)), q=1 .. floor((sqrt(2*N/5-1)-1)/2))}, list)); # Robert Israel, Mar 20 2018
MATHEMATICA
With[{nn=30}, Select[Union[Flatten[Table[(q^2+(q+1)^2)(r^2+(r+1)^2), {q, nn}, {r, q}]]], #<=5(nn^2+(nn+1)^2)&]] (* Harvey P. Dale, Jan 28 2019 *)
CROSSREFS
Sequence in context: A039376 A043199 A043979 * A020283 A350207 A211462
KEYWORD
nonn
STATUS
approved