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Triangular numbers whose external digits as well as internal digits form triangular numbers.
4

%I #7 Sep 19 2024 21:59:31

%S 0,1,3,6,10,15,21,28,36,45,55,66,78,91,105,231,435,465,666,1035,2211,

%T 3916,4005,6216,6786,19900,41905,46665,48205,162165,171405,200661,

%U 222111,329266,400065,1057785,1646205,2003001,2318781,2943951,10628355

%N Triangular numbers whose external digits as well as internal digits form triangular numbers.

%C Intersection of A077366 and A077367.

%Y Cf. A077366, A077367.

%K base,easy,nonn

%O 1,3

%A _Amarnath Murthy_, Nov 06 2002

%E Extended by _Ray Chandler_, Feb 28 2007

%E Offset changed by _Andrew Howroyd_, Sep 19 2024