OFFSET
1,1
LINKS
Chai Wah Wu, Table of n, a(n) for n = 1..2605
EXAMPLE
2457 is in the sequence because 2457 = 9^3+12^3, 2*2457 = 4914 = 1^3+17^3, 3*2457 = 7371 = 8^3+19^3 have at least one representation as a sum of two distinct positive cubes.
MAPLE
isA000578 := proc(n) option remember; local f; for f in ifactors(n)[2] do if op(2, f) mod 3 <> 0 then return false; end if; end do: true ; end proc:
isA024670 := proc(n) option remember ; local k, kc, k3 ; for k from 1 do k3 := k^3 ; kc := n-k^3 ; if kc <= k3 then return false; elif isA000578(kc) then return true; end if; end do: end proc:
isA191383 := proc(n) isA024670(n) and isA024670(2*n) and isA024670(3*n) ; end proc:
for n from 1 do if isA191383(n) then printf("%d, \n", n); end if; end do: # R. J. Mathar, Jun 03 2011
CROSSREFS
KEYWORD
nonn
AUTHOR
Zak Seidov, Jun 01 2011
STATUS
approved