A270672 Löschian numbers (A003136) that are multiples of 3.
0, 3, 9, 12, 21, 27, 36, 39, 48, 57, 63, 75, 81, 84, 93, 108, 111, 117, 129, 144, 147, 156, 171, 183, 189, 192, 201, 219, 225, 228, 237, 243, 252, 273, 279, 291, 300, 309, 324, 327, 333, 336, 351, 363, 372, 381, 387, 399, 417, 432, 441, 444, 453, 468, 471, 489, 507, 513, 516, 525, 543, 549
Offset: 1
Keywords
Examples
21 is a term because 21 = 3*7 = 4^2 + 4*1 + 1^2.
Links
- Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
Crossrefs
Programs
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Mathematica
Select[Range[0, 600], Resolve[Exists[{x, y}, Reduce[# == 3 (x^2 + x y + y^2), {x, y}, Integers]]] &] (* Michael De Vlieger, Mar 21 2016 *) -
PARI
x='x+O('x^1000); p=eta(x)^3/eta(x^3); for(n=0, 999, if(polcoeff(p, n) != 0 && n % 3 == 0, print1(n, ", "))); -
PARI
list(lim)=my(v=List(), y, t); for(x=0, sqrtint(lim\3), my(y=x, t); while((t=x^2+x*y+y^2)<=lim, listput(v, t); y+=3)); Set(v) \\ Charles R Greathouse IV, Jul 05 2017
Comments