OFFSET
1,2
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
s(14)=1+2+7=10 is a triangular number. In fact T(4)=10.
MAPLE
select(t -> issqr(1+8*(numtheory:-sigma(t)-t)), [$1..1000]); # Robert Israel, Dec 25 2016
MATHEMATICA
tri[ n_ ] := Module[ {}, a=Floor[ N[ Sqrt[ 2n ] ] ]; a(a+1)/2==n ]; Select[ Range[ 300 ], tri[ Apply[ Plus, Divisors[ # ] ]-# ]& ]
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
EXTENSIONS
More terms from Erich Friedman
STATUS
approved