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A349961 a(n) = Sum_{k=0..n} (2*n)^k. 1
1, 3, 21, 259, 4681, 111111, 3257437, 113522235, 4581298449, 210027483919, 10778947368421, 612142982430915, 38108188628928601, 2580398988131886039, 188802050194014479853, 14843696896551724137931, 1247923426698972051309601, 111713733654631566667971615 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
LINKS
FORMULA
a(n) = ((2*n)^(n+1) - 1)/(2*n - 1).
MATHEMATICA
a[0] = 1; a[n_] := Sum[(2*n)^k, {k, 0, n}]; Array[a, 18, 0] (* Amiram Eldar, Dec 07 2021 *)
PROG
(PARI) a(n) = sum(k=0, n, (2*n)^k);
(PARI) a(n) = ((2*n)^(n+1)-1)/(2*n-1);
CROSSREFS
Sequence in context: A317059 A262939 A232470 * A251573 A265002 A012131
KEYWORD
nonn,easy
AUTHOR
Seiichi Manyama, Dec 07 2021
STATUS
approved

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Last modified March 3 06:28 EST 2024. Contains 370499 sequences. (Running on oeis4.)