OFFSET
1,2
COMMENTS
Contains 4p for odd prime p if 3p-2 is a square, in particular if p is in A122430. - Robert Israel, Apr 13 2014
LINKS
Robert Israel, Table of n, a(n) for n = 1..2121
EXAMPLE
54 = 2*3^3 and 54 -(2+3) = 49 is a square, hence 54 is in the sequence.
MAPLE
filter:= proc(x) local y;
y:= x - add(i, i=numtheory:-factorset(x));
y > 0 and issqr(y)
end proc;
N:= 10000; # to get all entries <= N
A216894:= select(filter, [$1..N]); # Robert Israel, Apr 13 2014
MATHEMATICA
nspfQ[n_]:=Module[{c=n-Total[Transpose[FactorInteger[n]][[1]]]}, c>0 && IntegerQ[ Sqrt[c]]]; Join[{1}, Select[Range[10000], nspfQ]] (* Harvey P. Dale, Feb 12 2015 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Lagneau, Sep 19 2012
STATUS
approved