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A374144
a(n) is the smallest number which can be represented as the sum of two distinct nonzero n-gonal numbers in exactly n ways, or -1 if no such number exists.
4
81, 1105, 205427, 483031, 9402323, 6232341, 79324200, 768459127, 2265692766, 2413112833, 6737406626, 150437989675, 45319359337, 15140186701
OFFSET
3,1
LINKS
Eric Weisstein's World of Mathematics, Polygonal Number
Michael S. Branicky, Python program for A374144
EXAMPLE
a(3) = 81 = 3 + 78 = 15 + 66 = 36 + 45.
PROG
(Python) # see linked program
KEYWORD
nonn,more
AUTHOR
Ilya Gutkovskiy, Jun 28 2024
EXTENSIONS
a(9)-a(16) from Michael S. Branicky, Jun 30 2024
STATUS
approved