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A099137
Iterated pentagonal numbers starting with 2.
1
2, 5, 35, 1820, 4967690, 37016913420305, 2055377818749516111922729385, 6336866966711278058881411525857304983854251425952352645
OFFSET
0,1
LINKS
Eric Weisstein's World of Mathematics, Pentagonal Number
FORMULA
Let P(n) = n*(3*n-1)/2, a(1) = 2 and a(n) = P(a(n-1)) for n >= 2.
MATHEMATICA
NestList[PolygonalNumber[5, #]&, 2, 8] (* Harvey P. Dale, Sep 07 2024 *)
PROG
(PARI) a(n)=if(n==1, 2, a(n-1)*(3*a(n-1)-1)/2); \\ Joerg Arndt, Mar 05 2023
CROSSREFS
Sequence in context: A350955 A193323 A238752 * A309667 A059586 A160968
KEYWORD
easy,nonn
AUTHOR
Jonathan Vos Post, Nov 14 2004
EXTENSIONS
Edited by Giovanni Resta, Jun 17 2016
Edited by Joerg Arndt, Mar 05 2023
STATUS
approved