A363253 - OEIS

A363253

a(n) is the smallest n-gonal number which can be represented as the sum of distinct nonzero n-gonal numbers in exactly n ways, or -1 if no such number exists.

%I #7 Jun 02 2023 08:38:59

%S 28,121,210

%N a(n) is the smallest n-gonal number which can be represented as the sum of distinct nonzero n-gonal numbers in exactly n ways, or -1 if no such number exists.

%C a(8) = 736, a(9) = 969.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/PolygonalNumber.html">Polygonal Number</a>

%e For n = 3: 1 + 6 + 21 = 3 + 10 + 15 = 28.

%Y Cf. A057145, A350207, A350405, A350423.

%K nonn,bref,more,hard

%O 3,1

%A _Ilya Gutkovskiy_, May 23 2023