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A055049
Numbers of the form 5^(2*i+1)*(5*j+-2).
1
10, 15, 35, 40, 60, 65, 85, 90, 110, 115, 135, 140, 160, 165, 185, 190, 210, 215, 235, 240, 250, 260, 265, 285, 290, 310, 315, 335, 340, 360, 365, 375, 385, 390, 410, 415, 435, 440, 460, 465, 485, 490, 510, 515, 535, 540, 560, 565, 585, 590
OFFSET
1,1
COMMENTS
The numbers not of the form x^2+2y^2+5z^2.
LINKS
L. J. Mordell, A new Waring's problem with squares of linear forms, Quart. J. Math., 1 (1930), 276-288 (see p. 283).
FORMULA
a(n) ~ 12 * n. - David A. Corneth, Apr 12 2015
EXAMPLE
a(19) = a(1) + 25 * floor((19 - 1)/2) = 235 - David A. Corneth, Mar 31 2015
MAPLE
N:= 1000: # to get all terms <= N
A:= {}:
for i from 0 to floor((log[5](N)-1)/2) do
a:= 5^(2*i+1);
A:= A union {seq(a*(5*j+2), j=0..floor((N/a-2)/5))}
union {seq(a*(5*j-2), j=1..floor((N/a+2)/5))};
od:
A; # if using Maple 11 or earlier, uncomment the next line
# sort(convert(A, list)); # Robert Israel, Apr 13 2015
MATHEMATICA
Take[ Union@ Flatten@ Table[ 5^(2i + 1) (j), {i, 0, 1}, {j, Select[ Range@ 120, Mod[#, 5] == 2 || Mod[#, 5] == 3 &] }], 50] (* Robert G. Wilson v, Mar 30 2015 *)
PROG
(PARI) is(n) = v=valuation(n, 5); r=(n/5^v)%5; v%2==1&&(r==2||r==3) \\ David A. Corneth, Apr 12 2015
CROSSREFS
Sequence in context: A060535 A239595 A037379 * A128703 A276914 A078818
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jun 02 2000
STATUS
approved