A374141 - OEIS

A374141

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

%I #30 Jun 30 2024 22:11:40

%S 7,384,4995,51106,204805,483031,2443431,4674256,10476781,17272531,

%T 25600656,60765331,90406956,206602126,332808531,481676406,303826656,

%U 435211156,789949306,1406495106,2260173906,2704798281,3220562556,4435869181,5165053156,5309576106,9818788281

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

%H Michael S. Branicky, <a href="/A374141/b374141.txt">Table of n, a(n) for n = 1..39</a>

%H Michael S. Branicky, <a href="/A374141/a374141.txt">Python program for A374141, A374142, and A374143</a>

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

%e a(2) = 384 = 6 + 378 = 153 + 231.

%o (Python) # see linked program

%Y Cf. A000384, A093195, A332989, A342326, A374142, A374143.

%K nonn

%O 1,1

%A _Ilya Gutkovskiy_, Jun 28 2024

%E a(9)-a(27) from _Michael S. Branicky_, Jun 29 2024