A259746 - OEIS

A259746

Triangular numbers representable as x*y+x+y such that x and y are triangular numbers, x>=y>1.

%I #7 Jul 19 2015 12:03:21

%S 15,120,153,351,406,741,1891,3081,3403,4465,5151,5565,6555,9453,9591,

%T 18721,22791,38226,39903,46056,52326,79401,85491,91378,159895,187578,

%U 207690,222111,227475,229503,266815,274911,280875,326028,334971,354903,373680,410871,474825,609960

%N Triangular numbers representable as x*y+x+y such that x and y are triangular numbers, x>=y>1.

%C A subsequence of A000217, A254671 and A259745.

%C Up to 10^12, only 3 terms admit two representations, namely 22791, 410871 and 1675365. - _Giovanni Resta_, Jul 19 2015

%H Giovanni Resta, <a href="/A259746/b259746.txt">Table of n, a(n) for n = 1..500</a>

%e 153 = 6*21 + 6 + 21.

%e 351 = 15*21 + 15 + 21.

%e 406 = 10*36 + 10 + 36.

%Y Cf. A000217, A254671, A259745.

%K nonn

%O 1,1

%A _Alex Ratushnyak_, Jul 04 2015