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%I #18 Dec 01 2018 09:11:25
%S 27405,126225,194481,201825,273105,478401,538461,615681,718641,859600,
%T 862785,1056160,1187145,1257201,1328481,1413126,1439361,1532601,
%U 1540540,1619541,1625625,1708785,1842400,1849926,1890945
%N Numbers that have exactly 9 representations as a k-gonal number, P(n,k) = n*((k-2)*n - (k-4))/2, k and n >= 3.
%H Hugh Erling, <a href="/A321159/a321159.txt">Python program</a>
%e a(1) 27405 has representations P(n,k) = P(3, 9136)=P(5, 2742)=P(9, 763)=P(14, 303)=P(18, 181)=P(27, 80)=P(35, 48)=P(63, 16)=P(105, 7).
%e a(2) 126225 has representations P(n,k) = P(3, 42076)=P(5, 12624)=P(9, 3508)=P(15, 1204)=P(17, 930)=P(33, 241)=P(50, 105)=P(99, 28)=P(225, 7).
%e a(3) 194481 has representations P(n,k) = P(3, 64828)=P(6, 12967)=P(9, 5404)=P(14, 2139)=P(18, 1273)=P(21, 928)=P(27, 556)=P(81, 62)=P(441, 4).
%o (Python) See link
%o (PARI) isok(n) = sum(k=3, n-1, ispolygonal(n, k)) == 9; \\ _Michel Marcus_, Nov 02 2018
%Y Cf. A275256, A057145, A063778, A129654, A139601, A177029, A195527, A195528, A321156, A321157, A321158, A321160, A320943.
%K nonn
%O 1,1
%A _Hugh Erling_, Oct 29 2018
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