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A060182
a(0) = 1, a(1) = 5, a(2) = 13; a(n) = 2*a(n-1) + 2, n > 2.
2
1, 5, 13, 28, 58, 118, 238, 478, 958, 1918, 3838, 7678, 15358, 30718, 61438, 122878, 245758, 491518, 983038, 1966078, 3932158, 7864318, 15728638, 31457278, 62914558, 125829118, 251658238, 503316478, 1006632958, 2013265918
OFFSET
0,2
COMMENTS
Sometimes confused with A002717.
FORMULA
a(n) = 3(a(n-1) - a(n-2) + a(n-3) - ... ((-1)^(n+1))*a(0))+1;
a(n) = (2^(n-3))*a(3) + (2^(n-2)) - 2 for n > 3.
From R. J. Mathar, Jul 15 2009: (Start)
G.f.: -(1+x)*(x^2-x-1)/((-1+x)*(-1+2*x)).
a(n) = 15*2^(n-2) - 2, n > 1. (End)
PROG
(PARI) { a=-1; for (n=0, 200, a=2*a + 2; if (n<3, a++); write("b060182.txt", n, " ", a); ) } \\ Harry J. Smith, Jul 02 2009
CROSSREFS
Sequence in context: A027962 A023537 A023653 * A357945 A147066 A189485
KEYWORD
nonn,easy
AUTHOR
Brian Wallace (wallacebrianedward(AT)yahoo.co.uk), Mar 19 2001
EXTENSIONS
Simpler formula and more terms from Larry Reeves (larryr(AT)acm.org), Mar 30 2001
Edited by N. J. A. Sloane at the suggestion of Philippe LALLOUET (philip.lallouet(AT)wanadoo.fr), Sep 16 2007
STATUS
approved