%I #23 Sep 07 2024 19:50:46
%S 2,5,35,1820,4967690,37016913420305,2055377818749516111922729385,
%T 6336866966711278058881411525857304983854251425952352645
%N Iterated pentagonal numbers starting with 2.
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/PentagonalNumber.html">Pentagonal Number</a>
%F Let P(n) = n*(3*n-1)/2, a(1) = 2 and a(n) = P(a(n-1)) for n >= 2.
%t NestList[PolygonalNumber[5,#]&,2,8] (* _Harvey P. Dale_, Sep 07 2024 *)
%o (PARI) a(n)=if(n==1,2,a(n-1)*(3*a(n-1)-1)/2); \\ _Joerg Arndt_, Mar 05 2023
%Y Cf. A007501, A000326.
%K easy,nonn
%O 0,1
%A _Jonathan Vos Post_, Nov 14 2004
%E Edited by _Giovanni Resta_, Jun 17 2016
%E Edited by _Joerg Arndt_, Mar 05 2023