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A034478 a(n) = (5^n + 1)/2. 15
1, 3, 13, 63, 313, 1563, 7813, 39063, 195313, 976563, 4882813, 24414063, 122070313, 610351563, 3051757813, 15258789063, 76293945313, 381469726563, 1907348632813, 9536743164063, 47683715820313, 238418579101563 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Terms are also the quotients arising from sequence A050621.

Partial sums of A020699. - Paul Barry, Sep 03 2003

Binomial transform of A081294. - Paul Barry, Jan 13 2005

a(n)^2 + (a(n) - 1)^2 = a(2*n). E.g., 63^2 + 62^2 = 7813 = a(6). - Gary W. Adamson, Jun 17 2006

LINKS

Nathaniel Johnston, Table of n, a(n) for n = 0..250

FORMULA

E.g.f.: exp(3*x)*cosh(2*x). - Paul Barry, Mar 17 2003

O.g.f.: (1 - 3*x)/((1 - x)*(1 - 5*x)). - Paul Barry, Sep 03 2003

a(n) = Sum_{k=0..n} Sum_{j=0..k} binomial(n, k)*binomial(2*k, 2*j) - Paul Barry, Jan 13 2005

a(n) = 6*a(n-1) - 5*a(n-2) for n>1, a(0)=1, a(1)=3. - Philippe Deléham, Jul 11 2005

a(n) = 5*a(n-1) - 2 for n>0, a(0)=1. - Vincenzo Librandi, Aug 01 2010

EXAMPLE

G.f. = 1 + 3*x + 13*x^2 + 63*x^3 + 313*x^4 + 1563*x^5 + 7813*x^6 + ...

MAPLE

seq((5^n + 1)/2, n=0..20); # Zerinvary Lajos, Jun 16 2007

PROG

(Sage) [lucas_number2(n, 6, 5)/2 for n in xrange(0, 22)] # Zerinvary Lajos, Jul 08 2008

CROSSREFS

Cf. A050621.

Sequence in context: A276893 A284160 A092467 * A026715 A001850 A130525

Adjacent sequences:  A034475 A034476 A034477 * A034479 A034480 A034481

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified October 15 13:01 EDT 2018. Contains 316236 sequences. (Running on oeis4.)