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A015503 a(1)=1, a(n) = sum_{k=1}^{k=n-1} (4^k-1)/3 a(k). 0
1, 1, 6, 132, 11352, 3882384, 5303336544, 28966824203328, 632809241545903488, 55296137144764138588416, 19327437631660830304254690816, 27021729207700270170039091739231232, 151116480551518237100547636877027177224192 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..13.

FORMULA

a(n) = ((4^(n-1) + 2)/3) * a(n-1). - Vincenzo Librandi, Nov 11 2012

PROG

(MAGMA) I:=[1, 1, 6]; [n le 3 select I[n] else ((4^(n-1) + 2)/3) * Self(n-1): n in [1..15]]; // Vincenzo Librandi, Nov 11 2012

CROSSREFS

Sequence in context: A009688 A132872 A152289 * A350611 A247012 A003373

Adjacent sequences:  A015500 A015501 A015502 * A015504 A015505 A015506

KEYWORD

nonn,easy

AUTHOR

Olivier Gérard

STATUS

approved

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Last modified January 20 23:47 EST 2022. Contains 350473 sequences. (Running on oeis4.)