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A253579 Centered pentagonal numbers (A005891) which are also centered octagonal numbers (A016754). 3
1, 22801, 1666681, 47411143081, 3465632747641, 98584929298781641, 7206305041398228481, 204993755756525779060081, 14984516863488437537571601, 426256225957302372068628976801, 31158234954289838149958560780201, 886340998518823181233611960679431001 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
FORMULA
a(n) = a(n-1)+2079362*a(n-2)-2079362*a(n-3)-a(n-4)+a(n-5).
G.f.: -x*(x^4+22800*x^3-435482*x^2+22800*x+1) / ((x-1)*(x^2-1442*x+1)*(x^2+1442*x+1)).
EXAMPLE
22801 is in the sequence because it is the 96th centered pentagonal number and the 76th centered octagonal number.
PROG
(PARI) Vec(-x*(x^4+22800*x^3-435482*x^2+22800*x+1)/((x-1)*(x^2-1442*x+1)*(x^2+1442*x+1)) + O(x^100))
CROSSREFS
Sequence in context: A254087 A254094 A203065 * A197319 A263215 A263212
KEYWORD
nonn,easy
AUTHOR
Colin Barker, Jan 04 2015
STATUS
approved

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Last modified June 21 21:50 EDT 2024. Contains 373559 sequences. (Running on oeis4.)