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A217628 a(n) = 3^((n-1)*(n+2)/2). 2
1, 9, 243, 19683, 4782969, 3486784401, 7625597484987, 50031545098999707, 984770902183611232881, 58149737003040059690390169, 10301051460877537453973547267843, 5474401089420219382077155933569751763, 8727963568087712425891397479476727340041449 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..60

FORMULA

a(1) = 1, a(n) = a(n-1) * 3^n.

G.f.: G(0)/(2*x^3) - 1/(3*x)- 1/(3*x^2)- 1/(2*x^3), where G(k)= 1 + 3^(k-1)*x/(1 - 1/(1 + 1/G(k+1) )); (continued fraction). - Sergei N. Gladkovskii, Jul 28 2013

MATHEMATICA

Table[3^((n-1) * (n+2)/2), {n, 1, 30}]

PROG

(MAGMA) I:=[1]; [n le 1 select I[n] else Self(n-1)*3^n: n in [1..20]]

(Maxima) A217628[n]:=3^((n-1)*(n+2)/2)$

makelist(A217628[n], n, 1, 30); /* Martin Ettl, Oct 29 2012 */

CROSSREFS

Cf. A036442.

Sequence in context: A285511 A013733 A295228 * A167005 A112028 A183235

Adjacent sequences:  A217625 A217626 A217627 * A217629 A217630 A217631

KEYWORD

nonn

AUTHOR

Vincenzo Librandi, Oct 24 2012

STATUS

approved

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Last modified November 17 23:26 EST 2019. Contains 329242 sequences. (Running on oeis4.)