OFFSET
1,2
COMMENTS
Odd numbers n such that for all k with 1 <= k < sqrt(n), n - k^2 is not in A004215. - Robert Israel, Jan 24 2018
The only numbers for which allowing k = 0 would make a difference are 7 and 15: These two are not in A063954.
REFERENCES
J. H. Conway, personal communication, Aug 27, 2001.
FORMULA
MAPLE
isA004215:= proc(n)
local t;
t:= padic:-ordp(n, 2);
t::even and (n/2^t) mod 8 = 7
end proc:
filter:= proc(n) andmap(not(isA004215), [seq(n - k^2, k=1..floor(sqrt(n-1)))]) end proc:
select(filter, [seq(i, i=1..1000, 2)]); # Robert Israel, Jan 24 2018
MATHEMATICA
ok[n_] := Range[ Floor[ Sqrt[n] ]] == DeleteCases[ Union[ Flatten[ PowersRepresentations[n, 4, 2]]], 0, 1, 1]; A063951 = Select[ Range[1, 999, 2], ok] (* Jean-François Alcover, Sep 12 2012 *)
PROG
(PARI) is_A063951(n)=bittest(n, 0)&&!forstep(k=sqrtint(n-1), 1, -1, isA004215(n-k^2)&&return) \\ M. F. Hasler, Jan 26 2018
CROSSREFS
KEYWORD
nonn,easy,nice,fini,full
AUTHOR
N. J. A. Sloane, Sep 04 2001
STATUS
approved