OFFSET
1,1
COMMENTS
A triangular proper divisor of k is a positive triangular number less than k that divides k. - N. J. A. Sloane, Jul 04 2021
LINKS
Donovan Johnson, Table of n, a(n) for n = 1..300
EXAMPLE
5016 = 66*(66+6+3+1).
MATHEMATICA
pltQ[n_]:=Module[{d=Select[Divisors[n], OddQ[Sqrt[1+8#]]&]}, n == Total[ d] Last[d]]; Select[Range[2, 205000], pltQ] (* The program generates the first 7 terms of the sequence. To generate more, increase the Range constant. *) (* Harvey P. Dale, Jul 03 2021 *)
PROG
(PARI)
msumprop(n)={k=1; i=1; s=0; d=1; while(k<=n\2, if(n/k==n\k, d=k; s+=d); i+=1; k+=i); s*=d; return(s)}
{for (n=2, 10^7, if(n==msumprop(n), print(n)))}
CROSSREFS
KEYWORD
nonn
AUTHOR
Antonio Roldán, May 19 2013
STATUS
approved