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%I #14 Dec 10 2022 09:36:34
%S 64,925,2976,93457,866272,11025,3036880,18412718645101,9283470627432,
%T 201580440699781,92839099743040,5236660451226975,66779973961058176
%N a(n) is the smallest centered n-gonal number divisible by exactly n centered n-gonal numbers.
%C a(17) = 1415913990579036. - _Daniel Suteu_, Dec 10 2022
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/CenteredPolygonalNumber.html">Centered Polygonal Number</a>
%H <a href="/index/Di#divisors">Index entries for sequences related to divisors of numbers</a>
%e a(5) = 2976, because 2976 is a centered pentagonal number that has 5 centered pentagonal divisors {1, 6, 16, 31, 2976} and this is the smallest such number.
%o (PARI) a(n) = if(n<3, return()); for(k=1, oo, my(t=((n*k*(k+1))/2+1)); if(sumdiv(t, d, issquare(8*(d-1)/n + 1) && (sqrtint((8*(d-1))/n + 1)-1)%2 == 0) == n, return(t))); \\ _Daniel Suteu_, Dec 10 2022
%Y Cf. A005179, A358541, A358859, A358860.
%K nonn,more
%O 3,1
%A _Ilya Gutkovskiy_, Dec 03 2022
%E a(10)-a(15) from _Daniel Suteu_, Dec 06 2022